Method for transmitting and receiving data in wireless communication system and apparatus therefor

ABSTRACT

Particularly, the method performed by a first User Equipment includes receiving, from a base station, Downlink Control Information (DCI) including information related to a transmission of first control information; transmitting, to the second User Equipment, the first control information based on the received DCI; and transmitting, to the second User Equipment, one or more data through the sidelink.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2017/007049, filed on Jul. 3, 2017,which claims the benefit of U.S. Provisional Application No. 62/357,393filed on Jul. 1, 2016, the contents of which are all hereby incorporatedby reference herein in their entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method for transmitting and receiving databetween User Equipments in a wireless communication system that supportsVehicle-to-Everything (V2X) communication and an apparatus supportingthe same.

BACKGROUND ART

Mobile communication systems have been generally developed to providevoice services while guaranteeing user mobility. Such mobilecommunication systems have gradually expanded their coverage from voiceservices through data services up to high-speed data services. However,as current mobile communication systems suffer resource shortages andusers demand even higher-speed services, development of more advancedmobile communication systems is needed.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive multiple input multipleoutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An object of the present disclosure is to provide a method fortransmitting and receiving data through Sidelink between User Equipmentsin a wireless communication system that supports Vehicle-to-Everything(V2X) communication.

Particularly, an object of the present disclosure is to provide a methodfor determining data transmission timing based on Scheduling Assignment(SA) transmission timing in V2X communication.

In addition, an object of the present disclosure is to provide a methodfor determining data transmission timing based on DCI transmissiontiming in V2X communication.

In addition, an object of the present disclosure is to define a newfield for determining transmission timing between data in V2Xcommunication.

In addition, an object of the present disclosure is to apply either oneof scheduling considering a priority when dynamic scheduling andSemi-Persistent Scheduling (SPS) are scheduled simultaneously inrelation to a data transmission in V2X communication.

Technical objects to be achieved by the present invention are notlimited to the aforementioned technical objects, and other technicalobjects not described above may be evidently understood by a personhaving ordinary skill in the art to which the present invention pertainsfrom the following description.

Technical Solution

A method for transmitting data through sidelink in a wirelesscommunication system supporting Vehicle-to-Everything (V2X)communication according to the present disclosure includes receiving,from a base station, Downlink Control Information (DCI) includinginformation related to a transmission of first control information, thefirst control information is used for scheduling data transmitted to asecond User Equipment; transmitting, to the second User Equipment, thefirst control information based on the received DCI; and transmitting,to the second User Equipment, one or more data through the sidelink, theDCI is transmitted in subframe #n, the first control information istransmitted in subframe #n+k or in a specific sidelink subframegenerated after the subframe #n+k, and the DCI includes second controlinformation indicating a timing gap between a first data transmissionand a second data transmission.

In addition, in the present disclosure, the k is 4.

In addition, in the present disclosure, the first control informationand the one or more data are transmitted to the second User Equipment onan identical timing.

In addition, in the present disclosure, the identical timing is anidentical subframe.

In addition, in the present disclosure, the first data transmission isan initial transmission of data, and the second data transmission is aretransmission of data.

In addition, in the present disclosure, the first control information isa Scheduling Assignment (SA).

In addition, in the present disclosure, the second control informationis a timing gap field.

In addition, in the present disclosure, the first control informationincludes the second control information.

In addition, in the present disclosure, the specific sidelink subframeincludes initial sidelink subframes generated after the subframe #n+k.

In addition, in the present disclosure, when resource allocations forthe one or more data are scheduled simultaneously by Dynamic Schedulingand Semi-Persistent Scheduling (SPS), either one of the DynamicScheduling and the SPS is applied based on a specific criterion.

In addition, in the present disclosure, the specific criterion includesat least one of a length of transmission period of the SPS or animportance of transmission data.

A first User Equipment for transmitting data through sidelink in awireless communication system supporting Vehicle-to-Everything (V2X)communication according to the present disclosure includes a RadioFrequency (RF) unit configured to transmit and receive a radio signal;and a processor functionally connected with the RF unit, wherein theprocessor is configured to perform: receiving, from a base station,Downlink Control Information (DCI) including information related to atransmission of first control information, the first control informationis used for scheduling data transmitted to a second User Equipment;transmitting, to the second User Equipment, the first controlinformation based on the received DCI; and transmitting, to the secondUser Equipment, one or more data through the sidelink, the DCI istransmitted in subframe #n, the first control information is transmittedin subframe #n+k or in a specific sidelink subframe generated after thesubframe #n+k, and the DCI includes second control informationindicating a timing gap between a first data transmission and a seconddata transmission.

Technical Effects

According to an embodiment of the present invention, a timing on which adata transmission is started is clearly defined based on SA transmissiontiming or DCI transmission timing, and a problem of unable to transmitdata when failing to receive information for a data transmission timingfrom a base station.

In addition, according to an embodiment of the present invention,Time-Resource Pattern for Transmission (T-RPT) pattern which ispreviously used in relation to a data transmission inVehicle-to-Everything (V2X) communication is not used, but an indicatorindicating spacing between data transmissions is used, and there is aneffect of reducing a size of DCI.

Effects which may be obtained by the present invention are not limitedto the aforementioned effects, and other technical effects not describedabove may be evidently understood by a person having ordinary skill inthe art to which the present invention pertains from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the present invention and are incorporated in andconstitute a part of this application, illustrate embodiments of thepresent invention together with the detailed description serving todescribe the principle of the present invention.

FIG. 1 illustrates a radio frame structure in a wireless communicationsystem to which the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which the present invention may beapplied.

FIG. 3 illustrates a downlink subframe structure in a wirelesscommunication system to which the present invention may be applied.

FIG. 4 illustrates an uplink subframe structure in a wirelesscommunication system to which the present invention may be applied.

FIG. 5 is a diagram for schematically describing D2D communication in awireless communication system to which the present invention may beapplied.

FIG. 6 illustrates various scenarios of D2D communication in a wirelesscommunication system to which the method proposed in the presentdisclosure may be applied.

FIG. 7 illustrates protocol stack for Sidelink communication.

FIG. 8 illustrates control plane protocol stack for one-to-one Sidelinkcommunication to which the present invention may be applied.

FIG. 9 is a diagram for describing distributed discovery resourceallocation scheme in a wireless communication system supportingSidelink.

FIG. 10 illustrates Sidelink operation procedure in Sidelinkcommunication Mode 1 by a control of an eNB and a method for performingSidelink communication by transmitting and receiving the relatedinformation.

FIG. 11 illustrates a method for transmitting downlink controlinformation for Sidelink communication between UEs in a wirelesscommunication system supporting Sidelink.

FIG. 12 illustrates a type of V2X application to which the presentinvention may be applied.

FIG. 13 illustrates broadcast based V2V communication to which thepresent invention may be applied.

FIG. 14 illustrates examples of V2X operation mode based on only PC5interface.

FIG. 15 illustrates examples of V2X operation mode based on only Uuinterface.

FIG. 16 illustrates examples of V2X operation mode based on both of Uuinterface and PC5 interface.

FIG. 17 illustrates examples of scheduling scheme applicable to V2VSidelink communication.

FIG. 18 illustrates an example of SA transmission scheme.

FIG. 19 illustrates an operation flowchart for a first UE to transmitand receive data in a wireless communication system supportingVehicle-to-Everything (V2X).

FIG. 20 illustrates a method for determining a transmission timing ofdata using T-RPT pattern proposed in the present disclosure.

FIG. 21 illustrates another method for determining a transmission timingof data using T-RPT pattern proposed in the present disclosure.

FIG. 22 illustrates another method for determining a transmission timingof data using T-RPT pattern proposed in the present disclosure.

FIG. 23 is a flowchart illustrating an example of a method fortransmitting and receiving data in V2X Sidelink communication proposedin the present disclosure.

FIG. 24 illustrates a block diagram of a wireless communication deviceto which the methods proposed in the present disclosure may be applied.

FIG. 25 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present invention.

BEST MODE FOR INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Adetailed description to be disclosed below together with theaccompanying drawing is to describe embodiments of the present inventionand not to describe a unique embodiment for carrying out the presentinvention. The detailed description below includes details in order toprovide a complete understanding. However, those skilled in the art knowthat the present invention can be carried out without the details.

In some cases, in order to prevent a concept of the present inventionfrom being ambiguous, known structures and devices may be omitted or maybe illustrated in a block diagram format based on core function of eachstructure and device.

In the specification, a base station means a terminal node of a networkdirectly performing communication with a terminal. In the presentdocument, specific operations described to be performed by the basestation may be performed by an upper node of the base station in somecases. That is, it is apparent that in the network constituted bymultiple network nodes including the base station, various operationsperformed for communication with the terminal may be performed by thebase station or other network nodes other than the base station. A basestation (BS) may be generally substituted with terms such as a fixedstation, Node B, evolved-NodeB (eNB), a base transceiver system (BTS),an access point (AP), and the like. Further, a ‘terminal’ may be fixedor movable and be substituted with terms such as user equipment (UE), amobile station (MS), a user terminal (UT), a mobile subscriber station(MSS), a subscriber station (SS), an advanced mobile station (AMS), awireless terminal (WT), a Machine-Type Communication (MTC) device, aMachine-to-Machine (M2M) device, a Device-to-Device (D2D) device, andthe like.

Hereinafter, a downlink means communication from the base station to theterminal and an uplink means communication from the terminal to the basestation. In the downlink, a transmitter may be a part of the basestation and a receiver may be a part of the terminal. In the uplink, thetransmitter may be a part of the terminal and the receiver may be a partof the base station.

Specific terms used in the following description are provided to helpappreciating the present invention and the use of the specific terms maybe modified into other forms within the scope without departing from thetechnical spirit of the present invention.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), non-orthogonal multiple access (NOMA), and the like. The CDMAmay be implemented by radio technology universal terrestrial radioaccess (UTRA) or CDMA2000. The TDMA may be implemented by radiotechnology such as global system for mobile communications (GSM)/generalpacket radio service (GPRS)/enhanced data rates for GSM Evolution(EDGE). The OFDMA may be implemented as radio technology such as IEEE802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (Evolved UTRA),and the like. The UTRA is a part of a universal mobile telecommunicationsystem (UMTS). 3rd generation partnership project (3GPP) long termevolution (LTE) as a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) adopts the OFDMA in a downlink and theSC-FDMA in an uplink. LTE-advanced (A) is an evolution of the 3GPP LTE.

The embodiments of the present invention may be based on standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2 whichare the wireless access systems. That is, steps or parts which are notdescribed to definitely show the technical spirit of the presentinvention among the embodiments of the present invention may be based onthe documents. Further, all terms disclosed in the document may bedescribed by the standard document.

3GPP LTE/LTE-A is primarily described for clear description, buttechnical features of the present invention are not limited thereto.

(Terminology and Definition)

Carrier frequency: Center frequency of the cell

Cell: Combination of downlink and optionally uplink resources. Thelinking between the carrier frequency of the downlink resources and thecarrier frequency of the uplink resources is indicated in the systeminformation transmitted on the downlink resources.

Frequency layer: Set of cells with the same carrier frequency

Sidelink: UE to UE interface for Sidelink communication, V2X Sidelinkcommunication and Sidelink discovery

Sidelink Control period, SC period: Period over which resources areallocated in a cell for Sidelink control information and Sidelink datatransmissions

Sidelink communication: AS functionality enabling ProSe DirectCommunication between two or more nearby UEs, using E-UTRA technologybut not traversing any network node

Sidelink discovery: AS functionality enabling ProSe Direct Discoveryusing E-UTRA technology but not traversing any network node

Timing Advance Group, TAG: A group of serving cells that is configuredby RRC and that, for the cells with an UL configured, use the sametiming reference cell and the same Timing Advance value

V2X Sidelink communication: AS functionality enabling V2X Communicationbetween nearby UEs, using E-UTRA technology but not traversing anynetwork node

The following acronyms are applied for an object of the presentinvention.

ACK Acknowledgement

ARQ Automatic Repeat Request

CC Component Carrier

C-RNTI Cell RNTI

DCCH Dedicated Control Channel

DL Downlink

DwPTS Downlink Pilot Time Slot

eNB E-UTRAN NodeB

EPC Evolved Packet Core

EPS Evolved Packet System

E-RAB E-UTRAN Radio Access Bearer

E-UTRA Evolved UTRA

E-UTRAN Evolved UTRAN

FDD Frequency Division Duplex

FDM Frequency Division Multiplexing

LTE Long Term Evolution

MAC Medium Access Control

MCS Modulation and Coding Scheme

OFDM Orthogonal Frequency Division Multiplexing

OFDMA Orthogonal Frequency Division Multiple Access

ProSe Proximity based Services

PSBCH Physical Sidelink Broadcast CHannel

PSCCHPhysical Sidelink Control CHannel

PSDCHPhysical Sidelink Discovery CHannel

PSK Pre-Shared Key

PSSCH Physical Sidelink Shared CHannel

PUCCH Physical Uplink Control CHannel

PUSCHPhysical Uplink Shared CHannel

QoS Quality of Service

RRC Radio Resource Control

SI System Information

SIB System Information Block

SL-BCH Sidelink Broadcast Channel

SL-DCH Sidelink Discovery Channel

SL-RNTI Sidelink RNTI

SL-SCH Sidelink Shared Channel

STCH Sidelink Traffic Channel

TB Transport Block

TDD Time Division Duplex

TDM Time Division Multiplexing

TTI Transmission Time Interval

UE User Equipment

UL Uplink

UM Unacknowledged Mode

V2I Vehicle-to-Infrastructure

V2N Vehicle-to-Network

V2P Vehicle-to-Pedestrian

V2V Vehicle-to-Vehicle

V2X Vehicle-to-Everything

General System

FIG. 1 illustrates a structure a radio frame in a wireless communicationsystem to which the present invention can be applied.

In 3GPP LTE/LTE-A, radio frame structure type 1 may be applied tofrequency division duplex (FDD) and radio frame structure type 2 may beapplied to time division duplex (TDD) are supported.

In FIG. 1, the size of the radio frame in the time domain is representedby a multiple of a time unit of T_s=1/(15000*2048). The downlink anduplink transmissions are composed of radio frames having intervals ofT_f=307200*T_s=10 ms.

FIG. 1(a) illustrates the type 1 radio frame structure. The type 1 radioframe may be applied to both full duplex FDD and half duplex FDD.

The radio frame includes 10 subframes. One radio frame includes 20 slotseach having a length of T_slot=15360*T_s=0.5 ms. Indices 0 to 19 areassigned to the respective slots. One subframe includes two contiguousslots in the time domain, and a subframe i includes a slot 2i and a slot2i+1. The time taken to send one subframe is called a transmission timeinterval (TTI). For example, the length of one subframe may be 1 ms, andthe length of one slot may be 0.5 ms.

In FDD, uplink transmission and downlink transmission are classified inthe frequency domain. There is no restriction to full duplex FDD,whereas a UE is unable to perform transmission and reception at the sametime in a half duplex FDD operation.

One slot includes a plurality of orthogonal frequency divisionmultiplexing (OFDM) symbols in the time domain and includes a pluralityof resource blocks (RBs) in the frequency domain. An OFDM symbol is forexpressing one symbol period because 3GPP LTE uses OFDMA in downlink.The OFDM symbol may also be called an SC-FDMA symbol or a symbol period.The resource block is a resource allocation unit and includes aplurality of contiguous subcarriers in one slot.

FIG. 1(b) illustrates the type 2 radio frame structure. The type 2 radioframe structure includes 2 half frames each having a length of153600*T_s=5 ms. Each of the half frames includes 5 subframes eachhaving a length of 30720*T_s=1 ms.

In the type 2 radio frame structure of a TDD system, an uplink-downlinkconfiguration is a rule showing how uplink and downlink are allocated(or reserved) with respect to all of subframes. Table 1 represents theuplink-downlink configuration.

TABLE 1 Subframe number plink- ownlink-to-Uplink

Downlink Switch-point configuration periodicity ms

ms

ms

0ms

0ms

0ms

ms

indicates data missing or illegible when filed

Referring to Table 1, “D” indicates a subframe for downlinktransmission, “U” indicates a subframe for uplink transmission, and “S”indicates a special subframe including the three fields of a downlinkpilot time slot (DwPTS), a guard period (GP), and an uplink pilot timeslot (UpPTS) for each of the subframes of the radio frame.

The DwPTS is used for initial cell search, synchronization or channelestimation by a UE. The UpPTS is used for an eNB to perform channelestimation and for a UE to perform uplink transmission synchronization.The GP is an interval for removing interference occurring in uplink dueto the multi-path delay of a downlink signal between uplink anddownlink.

Each subframe i includes the slot 2i and the slot 2i+1 each having “Tslot=15360*T_s=0.5 ms.”

The uplink-downlink configuration may be divided into seven types. Thelocation and/or number of downlink subframes, special subframes, anduplink subframes are different in the seven types.

A point of time changed from downlink to uplink or a point of timechanged from uplink to downlink is called a switching point.Switch-point periodicity means a cycle in which a form in which anuplink subframe and a downlink subframe switch is repeated in the samemanner. The switch-point periodicity supports both 5 ms and 10 ms. Inthe case of a cycle of the 5 ms downlink-uplink switching point, thespecial subframe S is present in each half frame. In the case of thecycle of the 5 ms downlink-uplink switching point, the special subframeS is present only in the first half frame.

In all of the seven configurations, No. 0 and No. 5 subframes and DwPTSsare an interval for only downlink transmission. The UpPTSs, thesubframes, and a subframe subsequent to the subframes are always aninterval for uplink transmission.

Both an eNB and a UE may be aware of such uplink-downlink configurationsas system information. The eNB may notify the UE of a change in theuplink-downlink allocation state of a radio frame by sending only theindex of configuration information whenever uplink-downlinkconfiguration information is changed. Furthermore, the configurationinformation is a kind of downlink control information. Like schedulinginformation, the configuration information may be transmitted through aphysical downlink control channel (PDCCH) and may be transmitted to allof UEs within a cell in common through a broadcast channel as broadcastinformation.

Table 2 represents a configuration (i.e., the length of aDwPTS/GP/UpPTS) of the special subframe.

TABLE 2 Normal cyclic Extended cyclic prefix pecial prefix in downlinkin downlink subframe UpPT UpPTS configuration wPTS S wPTS ormal xtendedormal xtended cyclic cyclic cyclic cyclic prefix prefix prefix in prefixin in in uplink uplink uplink uplink

The structure of the radio frame according to the example of FIG. 1 isonly one example. The number of subcarriers included in one radio frame,the number of slots included in one subframe, and the number of OFDMsymbols included in one slot may be changed in various manners.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin the wireless communication system to which the present invention canbe applied.

Referring to FIG. 2, one downlink slot includes the plurality of OFDMsymbols in the time domain. Herein, it is exemplarily described that onedownlink slot includes 7 OFDM symbols and one resource block includes 12subcarriers in the frequency domain, but the present invention is notlimited thereto.

Each element on the resource grid is referred to as a resource elementand one resource block includes 12×7 resource elements. The number ofresource blocks included in the downlink slot, NDL is subordinated to adownlink transmission bandwidth.

A structure of the uplink slot may be the same as that of the downlinkslot.

FIG. 3 illustrates a structure of a downlink subframe in the wirelesscommunication system to which the present invention can be applied.

Referring to FIG. 3, a maximum of three former OFDM symbols in the firstslot of the sub frame is a control region to which control channels areallocated and residual OFDM symbols is a data region to which a physicaldownlink shared channel (PDSCH) is allocated. Examples of the downlinkcontrol channel used in the 3GPP LTE include a Physical Control FormatIndicator Channel (PCFICH), a Physical Downlink Control Channel (PDCCH),a Physical Hybrid-ARQ Indicator Channel (PHICH), and the like.

The PFCICH is transmitted in the first OFDM symbol of the subframe andtransports information on the number (that is, the size of the controlregion) of OFDM symbols used for transmitting the control channels inthe subframe. The PHICH which is a response channel to the uplinktransports an Acknowledgement (ACK)/Not-Acknowledgement (NACK) signalfor a hybrid automatic repeat request (HARQ). Control informationtransmitted through a PDCCH is referred to as downlink controlinformation (DCI). The downlink control information includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for apredetermined terminal group.

The PDCCH may transport A resource allocation and transmission format(also referred to as a downlink grant) of a downlink shared channel(DL-SCH), resource allocation information (also referred to as an uplinkgrant) of an uplink shared channel (UL-SCH), paging information in apaging channel (PCH), system information in the DL-SCH, resourceallocation for an upper-layer control message such as a random accessresponse transmitted in the PDSCH, an aggregate of transmission powercontrol commands for individual terminals in the predetermined terminalgroup, a voice over IP (VoIP). A plurality of PDCCHs may be transmittedin the control region and the terminal may monitor the plurality ofPDCCHs. The PDCCH is constituted by one or an aggregate of a pluralityof continuous control channel elements (CCEs). The CCE is a logicalallocation wise used to provide a coding rate depending on a state of aradio channel to the PDCCH. The CCEs correspond to a plurality ofresource element groups. A format of the PDCCH and a bit number ofusable PDCCH are determined according to an association between thenumber of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to betransmitted and attaches the control information to a cyclic redundancycheck (CRC) to the control information. The CRC is masked with a uniqueidentifier (referred to as a radio network temporary identifier (RNTI))according to an owner or a purpose of the PDCCH. In the case of a PDCCHfor a specific terminal, the unique identifier of the terminal, forexample, a cell-RNTI (C-RNTI) may be masked with the CRC. Alternatively,in the case of a PDCCH for the paging message, a paging indicationidentifier, for example, the CRC may be masked with a paging-RNTI(P-RNTI). In the case of a PDCCH for the system information, in moredetail, a system information block (SIB), the CRC may be masked with asystem information identifier, that is, a system information (SI)-RNTI.The CRC may be masked with a random access (RA)-RNTI in order toindicate the random access response which is a response to transmissionof a random access preamble.

Enhanced PDCCH (EPDCCH) carries UE-specific signaling. The EPDCCH islocated in a physical resource block (PRB) that is set to be terminalspecific. In other words, as described above, the PDCCH may betransmitted in up to three OFDM symbols in the first slot in thesubframe, but the EPDCCH may be transmitted in a resource region otherthan the PDCCH. The time (i.e., symbol) at which the EPDCCH in thesubframe starts may be set in the UE through higher layer signaling(e.g., RRC signaling, etc.).

The EPDCCH is a transport format, a resource allocation and HARQinformation associated with the DL-SCH and a transport format, aresource allocation and HARQ information associated with the UL-SCH, andresource allocation information associated with SL-SCH (Sidelink SharedChannel) and PSCCH Information, and so on. Multiple EPDCCHs may besupported and the terminal may monitor the set of EPCCHs.

The EPDCCH may be transmitted using one or more successive advanced CCEs(ECCEs), and the number of ECCEs per EPDCCH may be determined for eachEPDCCH format.

Each ECCE may be composed of a plurality of enhanced resource elementgroups (EREGs). EREG is used to define the mapping of ECCE to RE. Thereare 16 EREGs per PRB pair. All REs are numbered from 0 to 15 in theorder in which the frequency increases, except for the RE that carriesthe DMRS in each PRB pair.

The UE may monitor a plurality of EPDCCHs. For example, one or twoEPDCCH sets may be set in one PRB pair in which the terminal monitorsthe EPDCCH transmission.

Different coding rates may be realized for the EPOCH by mergingdifferent numbers of ECCEs. The EPOCH may use localized transmission ordistributed transmission, which may result in different mapping of theECCE to the REs in the PRB.

FIG. 4 illustrates a structure of an uplink subframe in the wirelesscommunication system to which the present invention can be applied.

Referring to FIG. 4, the uplink subframe may be divided into the controlregion and the data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) transporting uplink control information isallocated to the control region. A physical uplink shared channel(PUSCH) transporting user data is allocated to the data region. Oneterminal does not simultaneously transmit the PUCCH and the PUSCH inorder to maintain a single carrier characteristic.

A resource block (RB) pair in the subframe are allocated to the PUCCHfor one terminal. RBs included in the RB pair occupy differentsubcarriers in two slots, respectively. The RB pair allocated to thePUCCH is frequency-hopped in a slot boundary.

Device-to-Device (D2D) Communication

A device-to-device (D2D) communication or sidelink technology refers toa method of directly communicating with each other by geographicallyclose UEs without the intervention of infrastructure, such as a basestation. In the D2D communication technology, a technology chiefly usinga non-licensed frequency band, such as already commercialized Wi-FiDirect and Bluetooth, has been developed. However, for the purpose ofimproving frequency use efficiency of the cellular system, a D2Dcommunication technology using a licensed frequency band has beendeveloped and standardization thereof is performed.

In general, D2D communication is limitedly used as a term to refer tocommunication between things and thing intelligent communication.However, D2D communication in the present invention may include alltypes of communication between simple devices having a communicationfunction and various types of devices having a communication function,such as smartphones or personal computers.

D2D communication may also be called a sidelink or sidelinktransmission.

A sidelink includes sidelink discovery, sidelink communication, and V2Xsidelink communication between UEs.

FIG. 5 is a diagram for conceptually illustrating D2D communication in awireless communication system to which the present invention may beapplied.

FIG. 5(a) illustrates a communication method based on the existing eNB.A UE 1 may transmit data to the eNB on uplink, and the eNB may transmitdata to a UE 2 on downlink. Such a communication method may be called anindirect communication method through an eNB. In the indirectcommunication method, an Xn link (link between eNBs or link between aneNB and a relay and may be called a backhaul link), that is, a linkdefined in the existing wireless communication system and/or an Uu link(link between an eNB and a UE or link between a relay and a UE, and maybe called an access link) may be related.

FIG. 5(b) illustrates a UE-to-UE communication method as an example ofD2D communication. A data exchange between UEs may be performed withoutthe intervention of an eNB. Such a communication method may be called adirect communication method between devices. The D2D directcommunication method has advantages in that latency is reduced comparedto an indirect communication method through the existing eNB and lessradio resources are used.

FIG. 6 illustrates examples of various scenarios D2D communication towhich a method proposed in this specification may be applied.

The scenario of D2D communication may be basically divided into (1)Out-of-Coverage Network, (2) Partial-Coverage Network and (3)In-Coverage Network depending on whether a UE 1 and a UE 2 are locatedin-coverage/out-of-coverage.

In-Coverage Network may be divided into In-Coverage-Single-Cell andIn-Coverage-Multi-Cell based on the number of cells corresponding tocoverage of an eNB.

FIG. 6(a) illustrates an example of the Out-of-Coverage Network scenarioof D2D communication. The Out-of-Coverage Network scenario means thatD2D UEs perform D2D communication without control of an eNB. From FIG.6(a), it may be seen that only a UE 1 and a UE 2 are present and the UE1 and the UE 2 perform direct communication.

FIG. 6(b) illustrates an example of the Partial-Coverage Networkscenario of D2D communication. The Partial-Coverage Network scenariomeans that a D2D UE in coverage of a network and a D2D UE out ofcoverage of the network perform D2D communication. From FIG. 6(b), itmay be seen that a UE 1 in coverage of a network and a UE 2 out ofcoverage of the network communicate with each other.

FIG. 6(c) illustrates an example of the In-Coverage-Single-Cellscenario. FIG. 8(d) illustrates an example of the In-Coverage-Multi-Cellscenario. The In-Coverage Network scenario means that D2D UEs performD2D communication through control of an eNB in coverage of a network. InFIG. 6(c), a UE 1 and a UE 2 are located in the same network coverage(or cell) and perform D2D communication under the control of an eNB.

In FIG. 6(d), a UE 1 and a UE 2 are located in coverage of networks, butare located in coverage of different networks. Furthermore, the UE 1 andthe UE 2 perform D2D communication under the control of eNBs managingrespective network coverages.

Hereinafter, D2D communication or a sidelink are described morespecifically.

D2D communication may operate in the scenarios shown in FIG. 6. Ingeneral, D2D communication may operate in coverage of a network and outof coverage of a network. A link used for direct communication betweenUEs may be referred to as a sidelink, directlink or D2D link, but iscollectively called a sidelink, for convenience of description.

Sidelink transmission may operate in an uplink spectrum in the case ofFDD, and may operate in an uplink (or downlink) subframe in the case ofTDD. For the multiplexing sidelink transmission and uplink transmission,time division multiplexing (TDM) may be used.

Depending on the capability of a UE, sidelink transmission and uplinktransmission do not occur in a specific UE at the same time. Sidelinktransmission does not occur in an uplink subframe used for uplinktransmission or a sidelink subframe overlapping an UpPTS partially orfully. Furthermore, sidelink transmission and downlink transmission donot occur at the same time. Furthermore, the transmission and receptionof a sidelink do not occur at the same time.

The structure of a physical resource used for sidelink transmission maybe the same as the structure of an uplink physical resource. However,the last symbol of a sidelink subframe has a guard period and is notused for sidelink transmission.

A sidelink subframe may have an extended CP or a normal CP.

Sidelink communication may be basically divided into sidelink discovery,sidelink communication, sidelink synchronization, andvehicle-to-everything (V2X) sidelink communication.

Sidelink communication is communication mode in which a UE can performdirect communication through a PC5 interface. The communication mode issupported when a UE is served by an E-UTRAN and when a UE is out ofcoverage of E-UTRA.

Only UEs permitted to be used for a public safety operation may performsidelink communication.

In order to perform synchronization for an out-of-coverage operation, aUE(s) may operate as a synchronization source by transmitting a sidelinkbroadcast control channel (SBCCH) and a synchronization signal.

An SBCCH delivers the most important system information necessary toreceive a different sidelink channel and a signal. The SBCCH istransmitted in a fixed period of 40 ms along with a synchronizationsignal. When a UE is in network coverage, the contents of the SBCCH arederived or obtained from a parameter signaled by an eNB.

When a UE is out of coverage, if the UE selects another UE as asynchronization criterion, the contents of an SBCCH are derived from areceived SBCCH. If not, the UE uses a pre-configured parameter. A systeminformation block (SIB) 18 provides a synchronization signal andresource information for SBCCH transmission.

For an out-of-coverage operation, two pre-configured subframes arepresent every 40 ms. A UE receives a synchronization signal and SBCCH inone subframe. When the UE becomes a synchronization source based on adefined criterion, it transmits a synchronization signal and SBCCH inanother subframe.

A UE performs sidelink communication on defined subframes during asidelink control period. The sidelink control period is the period inwhich resources allocated to a cell occur for sidelink controlinformation and sidelink data transmission. The UE transmits sidelinkcontrol information and sidelink data within the sidelink controlperiod.

The sidelink control information indicates a layer 1 ID and transmissioncharacteristics (e.g., MCS, the location of a resource for a sidelinkcontrol period and timing alignment).

A UE performs transmission/reception through the Uu and PC5 in order ofthe following lower priority if a sidelink discovery gap has not beenconfigured.

-   -   Uu transmission/reception (highest priority);    -   PC5 sidelink communication transmission and reception;    -   PC5 sidelink discovery announcement/monitoring (lowest        priority).

A UE performs transmission and reception through the Uu and PC5 in orderof the following lower priority if a sidelink discovery gap has beenconfigured:

-   -   Uu transmission/reception for RACH;    -   PC5 sidelink discovery announcement during a Sidelink Discovery        Gap for transmission;    -   Non-RACH Uu transmission;    -   PC5 sidelink discovery monitoring during a Sidelink Discovery        Gap for reception;    -   Non-RACH Uu reception;    -   PC5 sidelink communication transmission and reception.

Sidelink Radio Protocol Structure

A UE radio protocol structure for sidelink communication with respect toa user plane and a control plane is described.

FIG. 7 illustrates a protocol stack for sidelink communication.

Specifically, FIG. 7(a) illustrates a protocol stack for a user plane inwhich a PDCP, RLC and MAC sublayer (end in another UE) perform functionson a user plane. The access layer protocol stack of a PC5 interfaceincludes a PDCP, RLC, MAC and PHY as shown in FIG. 7(a).

User plane detailed information of sidelink communication:

-   -   There is no HARQ feedback for sidelink communication.    -   RLC UM is used for sidelink communication.    -   A receiver UE needs to maintain at least one RLC UM entity every        transmission peer UE.    -   A reception RLC UM entity used for sidelink communication does        not need to be configured prior to the reception of a first RLC        UMD PDU.    -   ROHC unidirectional mode is used for the header compression of a        PDCP for additional communication.

A UE may configure a plurality of logical channels. An LCID included ina MAC subheader uniquely identifies a logical channel within the rangeof one Source Layer-2 ID and Destination Layer-2 ID combination. Aparameter for logical channel priority is not configured.

An access layer (AS) is provided along with a ProSe Per-Packet Priority(PPPP) of a protocol data unit transmitted through the PC5 interface ina higher layer. There is a PPPP related to each logical channel.

A UE configures and does not maintain a logical connection to receiverUEs prior to one-to-multiple sidelink communication. A higher layerconfigures and maintains a logical connection for one-to-one sidelinkcommunication, including a ProSe UE-to-Network Relay task.

FIG. 7(b) illustrates a control plane protocol stack for an SBCCH towhich the present invention may be applied. In the PC5 interface, anaccess layer protocol stack for an SBCCH includes RRC, RLC, MAC and PHYas in FIG. 7(b).

A control plane for configuring, maintaining and releasing a logicalconnection for one-to-one sidelink communication is shown in FIG. 8.

FIG. 8 illustrates a control plane protocol stack for one-to-onesidelink communication to which the present invention may be applied.

Sidelink Discovery

In sidelink communication, since a plurality of transmitter/receiver UEsis distributed at a given location, a sidelink discovery procedure forconfirming the presence of surrounding UEs is necessary before aspecific UE perform sidelink communication with surrounding UEs.Furthermore, sidelink discovery may be used to confirm the presence ofsurrounding UEs and used for various commercial purposes, such asadvertising, issuing coupons and finding friends, with respect to UEswithin a proximity area.

Sidelink discovery may be applied within network coverage (includinginter-cell, intra-cell). In inter-cell discovery, both synchronous andasynchronous cell deployments may be taken into consideration.

In this case, a signal (or message) periodically transmitted by UEs forsidelink discovery may be referred to as a discovery message, discoverysignal, a beacon, etc. Hereinafter, a signal periodically transmitted byUEs for sidelink discovery is collectively called a discovery message,for convenience of description.

If a UE 1 has the role of discovery message transmission, the UE 1transmits a discovery message, and a UE 2 receives the discoverymessage. The transmission and reception roles of the UE 1 and the UE 2may be changed. Transmission from the UE 1 may be received by one ormore UE(s), such as the UE 2.

A discovery message may include a single MAC PDU. In this case, thesingle MAC PDU may include a UE ID and an application ID.

A physical sidelink discovery channel (PSDCH) may be defined as achannel in which a discovery message is transmitted. The structure of aPSDCH channel may reuse a PUSCH structure.

Two types (sidelink discovery type 1 and sidelink discovery type 2B) maybe used as a resource allocation method for sidelink discovery.

In the case of the sidelink discovery type 1, an eNB may allocate aresource for discovery message transmission in a non-UE-specific manner.

Specifically, a radio resource pool (i.e., discovery pool) for discoverytransmission and reception, including a plurality of subframe sets and aplurality of resource block sets, is allocated within a specific period(hereinafter “discovery period”). A discovery transmitter UE randomlyselects a specific resource within the radio resource pool and thentransmits a discovery message.

Such a periodical discovery resource pool may be allocated for discoverysignal transmission in a semi-static manner. Configuration informationof a discovery resource pool for discovery transmission includes adiscovery period, a subframe set which may be used for the transmissionof a discovery signal within a discovery period, and resource block setinformation.

Such configuration information of a discovery resource pool may betransmitted to a UE by higher layer signaling. In the case of anin-coverage UE, a discovery resource pool for discovery transmission isconfigured by an eNB, and a UE may be notified of the discovery resourcepool through RRC signaling (e.g., a system information block (SIB)).

A discovery resource pool allocated for discovery within one discoveryperiod may be multiplexed with a time-frequency resource block havingthe same size through TDM and/or FDM. A time-frequency resource blockhaving the same size may be referred to as a “discovery resource.” Adiscovery resource may be divided as one subframe unit, and may includetwo physical resource blocks (PRBs) per slot in each subframe. Onediscovery resource may be used for the transmission of a discovery MACPDU by one UE.

Furthermore, a UE may repeatedly transmit a discovery signal within adiscovery period for the transmission of one transport block. Thetransmission of a MAC PDU transmitted by one UE may be repeated (e.g.,repeated four times) contiguously or non-contiguously within a discoveryperiod (i.e., radio resource pool). The number of transmissions of adiscovery signal for one transport block may be transmitted by a UEthrough higher layer signaling.

A UE randomly selects the first discovery resource in a discoveryresource set which may be used for the repeated transmission of a MACPDU. Other discovery resources may be determined in relation to thefirst discovery resource. For example, a specific pattern may bepre-configured, and a next discovery resource may be determinedaccording to a pre-configured pattern based on the location of adiscovery resource first selected by a UE. Furthermore, the UE mayrandomly select each discovery resource within a discovery resource setwhich may be used for the repeated transmission of a MAC PDU.

In the sidelink discovery type 2, a resource for discovery messagetransmission is allocated in a UE-specific manner. Type 2 is subdividedinto Type 2A and Type 2B. Type 2A is a method in which an eNB allocatesa resource at each transmission instance of a discovery message by a UEwithin a discovery period. Type 2B is a method of allocating a resourcein a semi-persistent manner.

In the case of the sidelink discovery type 2B, a RRC_CONNECTED UErequests the allocation of a resource for the transmission of a sidelinkdiscovery message from an eNB through RRC signaling. Furthermore, theeNB may allocate the resource through RRC signaling. When the UE makestransition to an RRC_IDLE state or the eNB withdraws resource allocationthrough RRC signaling, the UE releases the most recently allocatedtransmission resource. As described above, in the case of the sidelinkdiscovery type 2B, a radio resource may be allocated by RRC signaling,and the activation/deactivation of radio resources allocated by a PDCCHmay be determined.

A radio resource pool for discovery message reception is configured byan eNB, and a UE may be notified of the radio resource pool using RRCsignaling (e.g., a system information block (SIB)).

A discovery message receiver UE monitors both the discovery resourcepools of the sidelink discovery type 1 and type 2 for discovery messagereception.

A sidelink discovery method may be divided into a centralized discoverymethod assisted by a central node, such as an eNB, and a distributeddiscovery method for a UE autonomously to confirm the presence of asurrounding UE without the help of a central node.

In this case, in the case of the distributed discovery method, adedicated resource may be periodically allocated separately from acellular resource as a resource for a UE to transmit and receivediscovery messages.

FIG. 9 is a diagram for illustrating a distributed discovery resourceallocation method in a wireless communication system supporting asidelink.

Referring to FIG. 9, in the distributed discovery method, a discoverysubframe (i.e., “discovery resource pool”) 901 for discovery among allcellular uplink frequency-time resources is fixedly (or dedicatedly)allocated, and the remaining region may include the existing LTE uplinkwide area network (WAN) subframe region 902. The discovery resource poolmay include one or more subframes.

The discovery resource pool may be periodically allocated at a specifictime interval (i.e., “discovery period” or “PSDCH period”). Furthermore,the discovery resource pool may be repeatedly configured within onediscovery period.

FIG. 9 illustrates an example in which a discovery resource pool isallocated with a discovery period of 10 sec and 64 contiguous subframesare allocated in each discovery resource pool. However, the sizes of adiscovery period and time/frequency resource of a discovery resourcepool correspond to example, and the present invention is not limitedthereto.

A UE autonomously selects a resource (i.e., “discovery resource”) fortransmitting its own discovery message within a dedicatedly allocateddiscovery pool, and transmits a discovery message through the selectedresource.

Sidelink Communication

The application area of sidelink communication also includes networkedge-of-coverage in addition to in and out of network coverage(in-coverage, out-of-coverage). Sidelink communication may be used forpurposes, such as public safety (PS).

If a UE 1 has the role of direct communication data transmission, the

UE 1 transmits direct communication data, and a UE 2 receives directcommunication data. The transmission and reception roles of the UE 1 andthe UE 2 may be changed. Direct communication transmission from the UE 1may be received by one or more UE(s), such as the UE 2.

Sidelink discovery and sidelink communication are not associated, butmay be independently defined. That is, in groupcast and broadcast directcommunication, sidelink discovery is not necessary. As described above,if sidelink discovery and sidelink direct communication areindependently defined, UEs do not need to recognize an adjacent UE. Inother words, in the case of groupcast and broadcast directcommunication, all receiver UEs within a group do not need to beadjacent to each other.

A physical sidelink shared channel (PSSCH) may be defined as a channelin which sidelink communication data is transmitted. Furthermore, aphysical sidelink control channel (PSCCH) may be defined as a channel inwhich control information for sidelink communication (e.g., schedulingassignment (SA) for sidelink communication data transmission,transmission format) is transmitted. A PSSCH and a PSCCH may reuse aPUSCH structure.

Two modes (Mode 1, Mode 2) may be used as a resource allocation methodfor sidelink communication.

Mode 1 refers to a method of an eNB to schedule resources, used totransmit data or control information for sidelink communication, withrespect to a UE. In in-coverage, Mode 1 is applied.

An eNB configures a resource pool for sidelink communication. The eNBmay deliver information on a resource pool for sidelink communication tothe UE through higher layer signaling. In this case, the resource poolfor sidelink communication may be divided into a control informationpool (i.e., resource pool for transmitting a PSCCH) and a sidelink datapool (i.e., resource pool for transmitting a PSSCH).

When a transmitter UE requests a resource for transmitting controlinformation and/or data from an eNB, the eNB schedules a controlinformation and sidelink data transmission resource within a poolconfigured in the transmitter D2D UE using a PDCCH or ePDCCH.Accordingly, the transmitter UE transmits control information andsidelink data to a receiver UE using the scheduled (i.e., allocated)resource.

Specifically, the eNB may perform scheduling on a resource fortransmitting control information (i.e., resource for transmitting aPSCCH) using a downlink control information (DCI) format 5 or a DCIformat 5A, and may perform scheduling on a resource for transmittingsidelink data (i.e., resource for transmitting a PSSCH) using a sidelinkcontrol information (SCI) format 0 or an SCI format 1. In this case, theDCI format 5 includes some fields of the SCI format 0, and the DCIformat 5A includes some fields of the SCI format 1.

In accordance with the above description, in the case of Mode 1, atransmitter UE needs to be in the RRC_CONNECTED state in order toperform sidelink communication. The transmitter UE transmits ascheduling request to an eNB. A buffer status report (BSR) procedure isperformed so that an eNB can determine the amount of resources requestedby the transmitter UE.

When receiver UEs monitor a control information pool and decode controlinformation related thereto, they may selectively decode sidelink datatransmission related to the corresponding control information. Thereceiver UE may not decode a sidelink data pool based on a result of thedecoding of control information.

A detailed example and signaling procedure of the sidelink communicationmode 1 are shown in FIGS. 10 and 11. In this case, as described above,control information related to sidelink communication is transmittedthrough a PSCCH, and data information related to sidelink communicationis transmitted through a PSSCH.

FIG. 10 illustrates a method of performing a sidelink operationalprocedure in a sidelink communication mode 1 based on control of an eNBand sidelink communication by transmitting and receiving relatedinformation.

As shown in FIG. 10, a PSCCH resource pool 1010 and/or a PSSCH resourcepool 1020 related to sidelink communication may be pre-configured. Thepre-configured resource pool may be transmitted from an eNB to sidelinkUEs through higher layer signaling (e.g., RRC signaling). In this case,the PSCCH resource pool and/or the PSSCH resource pool may mean aresource (i.e., dedicated resource) reserved for sidelink communication.In this case, the PSCCH is control information for scheduling thetransmission of sidelink data (i.e., PSSCH), and may mean a channel inwhich the SCI format 0 is transmitted.

Furthermore, the PSCCH is transmitted according to a PSCCH period, andthe PSSCH is transmitted according to a PSSCH period. The scheduling ofthe PSCCH is performed through the DCI format 5 (or DCI format 5A), andthe scheduling of the PSSCH is performed through the SCI format 0 (orSCI format 1). The DCI format 5 may be referred to as a sidelink grant,and may be transmitted through a physical layer channel or MAC layerchannel, such as a PDCCH or an EPDCCH.

In this case, the DCI format 5 includes resource information for a PSCCH(i.e., resource allocation information), a transmission power control(TPC) command for a PSCCH and PSSCH, a zero padding (ZP) bit(s) and somefields of the SCI format 0 (e.g., frequency hopping flag, resource blockassignment and hopping resource allocation information, a time resourcepattern (e.g., subframe pattern)).

Furthermore, the fields of the SCI format 0 is information related tothe scheduling of a PSSCH, and includes fields, such as a frequencyhopping flag, a time resource pattern, a modulation and coding scheme(MCS), a TA indication, and a group destination ID.

FIG. 11 illustrates a downlink control information transmission methodfor sidelink communication between UEs in a wireless communicationsystem supporting sidelink communication. FIG. 11 is merely forconvenience of description and does not limit the scope of the presentinvention.

Referring to FIG. 11, it is assumed that the DCI format 5 is used as asidelink grant. If the DCI format 5A is used, in FIG. 11, the DCI format5 is substituted with a DCI format 5A and the SCI format 0 may besubstituted with the SCI format 1.

First, in step S1105, a PSCCH resource pool and/or a PSSCH resource poolrelated to a sidelink is configured by a higher layer.

Thereafter, in step S1110, an eNB transmits information on the PSCCHresource pool and/or the PSSCH resource pool to a sidelink UE throughhigher layer signaling (e.g., RRC signaling).

Thereafter, in step S1115, the eNB transmits control information,related to the transmission of a PSCCH (i.e., SCI format 0) and/or thetransmission of a PSSCH (i.e., sidelink communication data), to asidelink transmitter UE through the DCI format 5 respectively ortogether. The control information includes information scheduling of thePSCCH and/or the PSSCH in the PSCCH resource pool and/or the PSSCHresource pool. For example, resource allocation information, an MCSlevel, a time resource pattern, etc. may be included in the controlinformation.

Thereafter, in step S1120, the sidelink transmitter UE transmits thePSCCH (i.e., SCI format 0) and/or PSSCH (i.e., sidelink communicationdata) to a sidelink receiver UE based on the information received instep S1115. In this case, the transmission of the PSCCH and thetransmission of the PSSCH may be performed together, or the transmissionof the PSSCH may be performed after the transmission of the PSCCH.

Meanwhile, although not shown in FIG. 11, the sidelink transmitter UEmay request a transmission resource (i.e., PSSCH resource) for sidelinkdata from the eNB, and the eNB may schedule resources for thetransmission of the PSCCH and the PSSCH. To this end, the sidelinktransmitter UE transmits a scheduling request (SR) to the eNB, and abuffer status report (BSR) procedure may be performed so that the eNBcan determine the amount of resources requested by the sidelinktransmitter UE.

Sidelink receiver UEs may monitor a control information pool. Whencontrol information related thereto is decoded, the sidelink receiverUEs may selectively decode sidelink data transmission related to thecorresponding control information.

In contrast, Mode 2 refers to a method of a UE to randomly select aspecific resource in a resource pool in order to transmit data orcontrol information for sidelink communication. In out-of-coverageand/or in-coverage, Mode 2 is applied.

In Mode 2, a resource pool for control information transmission and/or aresource pool for sidelink communication data transmission may bepre-configured or may be semi-statically configured. A UE is providedwith a configured resource pool (time and frequency) and selects aresource for sidelink communication transmission in a resource pool.That is, the UE may select a resource for control informationtransmission in a control information resource pool in order to transmitcontrol information. Furthermore, the UE may select a resource in a dataresource pool for the sidelink communication data transmission.

Furthermore, in sidelink broadcast communication, control information istransmitted by a broadcasting UE. The control information explicitlyand/or implicitly indicates the location of a resource for datareception in relation to a physical channel (i.e., PSSCH) that carriessidelink communication data.

Sidelink Synchronization

A sidelink synchronization signal (sidelink synchronization sequence,sidelink SS) may be used for a UE to obtain time-frequencysynchronization. In particular, in the case of out of coverage of anetwork, control of an eNB is impossible. A new signal and procedure forsynchronization establishment between UEs may be defined.

A UE that periodically transmits a sidelink synchronization signal maybe referred to as a sidelink synchronization source.

Each UE may have multiple physical-layer sidelink synchronizationidentities (IDs). The number of physical-layer sidelink synchronizationIDs is 336 (i.e., 0 to 335). 336 physical-layer sidelink synchronizationIDs may be divided into an in-network coverage part ID set (id_net set,0 to 167) and an out-of-network coverage ID set (id_oon set, 168 to335).

A sidelink synchronization signal includes a primary sidelinksynchronization signal (PSSS) and a secondary sidelink synchronizationsignal (SSSS).

The PSSS is transmitted in two neighbor SC-FDMA symbols of the samesubframe. In this case, in order to generate the PSSS, if physical-layersidelink synchronization IDs are 0 to 167, a Zadoff-Chu sequence havinga root index of 26 is used. In other cases, a Zadoff-Chu sequence havinga root index of 37 is used.

In this case, a sequence configuring the PSSS is mapped to the resourceelements of an antenna port 1020 in the first slot of a correspondingsubframe according to Equation 1.

$\begin{matrix}{{{a_{k,l} = {d_{i}(n)}},{n = 0},\ldots \mspace{14mu},61}{k = {n - 31 + \frac{N_{RB}^{SL}N_{sc}^{RB}}{2}}}{l = \left\{ \begin{matrix}{1,2} & {{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}} \\{0,1} & {{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

Furthermore, the SSSS is transmitted in the two neighbor SC-FDMA symbolsof the same subframe. In this case, in order to generate the SSSS, twosequences assuming a subframe 0, that is, N_(ID) ⁽¹⁾=N_(ID) ^(SL) mod168 and N_(ID) ⁽²⁾=└N_(ID) ^(SL)/168┘ for transmission modes 1 and 2,and a subframe 5 for transmission modes 3 and 4, respectively, are used.

In this case, a sequence configuring the SSSS is mapped to resourceelements for the antenna port 1020 in the second slot of a correspondingsubframe according to Equation 2.

$\begin{matrix}{{{a_{k,l} = {d_{i}(n)}},{n = 0},\ldots \mspace{14mu},61}{k = {n - 31 + \frac{N_{RB}^{SL}N_{sc}^{RB}}{2}}}{l = \left\{ \begin{matrix}{4,5} & {{normal}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}} \\{3,4} & {{extended}\mspace{14mu} {cyclic}\mspace{14mu} {prefix}}\end{matrix} \right.}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

Before transmitting a sidelink synchronization signal, a UE may discovera sidelink synchronization source. Furthermore, when the sidelinksynchronization source is discovered, the UE may obtain time-frequencysynchronization through the received sidelink synchronization signalfrom the discovered sidelink synchronization source. Furthermore, thecorresponding UE may transmit a sidelink synchronization signal.

Furthermore, a channel for delivering system information used forcommunication between UEs and synchronization-related information alongwith synchronization may be necessary. The channel may be referred to asa physical sidelink broadcast channel (PSBCH).

Vehicle-to-Everything (V2X)

(1) Vehicle-to-Everything (V2X) Sidelink Communication

V2X sidelink communication includes communication between a vehicle andall entities, such as vehicle-to-vehicle (V2V) referring tocommunication between vehicles, vehicle to infrastructure (V2I)referring communication between a vehicle and an eNB or a road side unit(RSU), and vehicle-to-pedestrian (V2P) referring to communicationbetween a vehicle and UEs owned by persons (pedestrian, bicycler,vehicle driver or passenger).

In this case, a wireless communication system supporting V2X sidelinkcommunication may include specific network entities for supportingcommunication between a vehicle and all entities. For example, thenetwork entity may be an eNB, road side unit (RSU), a UE or anapplication server (e.g., traffic safety server).

Furthermore, a UE performing V2X sidelink communication may mean avehicle UE (V-UE), a pedestrian UE, an RSU of an eNB type or an RSU of aUE type in addition to a common handheld UE.

V2X sidelink communication may be directly performed between UEs or maybe performed through a network entity(s). V2X operation modes may beclassified according to a method of performing V2X sidelinkcommunication.

Terms used in V2X are defined as follows.

A road side unit (RSU): a road side unit (RSU) is a V2X service-capableapparatus capable of transmission and reception to and from a movingvehicle using V2I service.

Furthermore, the RSU is a fixed infrastructure entity supporting a V2Xapplication program and may exchange messages with other entitiessupporting a V2X application program.

Pseudonymity: a condition in which data is not provided to a specificsubscriber without using additional information in the processing ofpersonally identifiable information (PII). A technological andorganization measures for separately maintaining such additionalinformation and guaranteeing non-attribution for a subscriber that hasbeen identified or that may be identified.

The RSU is a term frequently used in the existing ITS spec. The reasonwhy the term is introduced into 3GPP spec. is for enabling the documentto be read more easily in the ITS industry.

The RSU is a logical entity that combines V2X application logic with thefunction of an eNB (called eNB-type RSU) or a UE (called UE-type RSU).

V2I Service: type of V2X service and an entity having one side belongingto a vehicle and the other side belonging to infrastructure.

V2P Service: V2X service type in which one side is a vehicle and theother side is a device carried by a person (e.g., a portable devicecarried by a pedestrian, bicycler, driver or follow passenger).

V2X Service: 3GPP communication service type in which a transmission orreception device is related to a vehicle.

V2V service, V2I service and V2P service may be further classifieddepending on a counterpart who participates in communication.

V2X enabled UE: UE supporting V2X service.

V2V Service: type of V2X service in which both sides of communicationare vehicles.

V2V communication range: a direct communication range between twovehicles participating in V2V service.

V2X application program support type

A V2X application called vehicle-to-everything (V2X), as describedabove, includes the four types of (1) vehicle-to-vehicle (V2V), (2)vehicle-to-infrastructure (V2I), (3) vehicle-to-network (V2N) and (4)vehicle-to-pedestrian (V2P).

FIG. 12 illustrates the type of V2X application to which the presentinvention may be applied.

The four types of a V2X application may use “co-operative awareness”providing more intelligent service for the final user.

This means that entities, such as a vehicle, roadside infrastructure, anapplication server and a pedestrian, can collect knowledge of acorresponding area environment (e.g., information received from otheradjacent vehicle or sensor device) so that the entities can process andshare the corresponding knowledge in order to provide more intelligentinformation, such as a cooperative collision warning or autonomousdriving.

Furthermore, the V2V applications expect adjacent UEs to exchange V2Vapplication information. The 3GPP transmission of a message includingV2V application information requires a UE to obtain valid subscriptionand permission from a network operator.

Transmission for a valid subscriber is provided regardless of whether aUE is served by an E-UTRAN. A UE supporting the V2V applicationtransmits a message including 2V application information (e.g.,location, dynamic and attributes). Message payload may be flexible inorder to accommodate the amount of various types of information.

The 3GPP transmission of a message including V2V application informationis chiefly based on broadcast as shown in FIG. 13. Such 3GPPtransmission includes direct transmission between UEs due to arestricted direct communication range and/or transmission between UEsthrough a base structure supporting V2X communication, such as RSX andapplication server.

FIG. 13 illustrates broadcast-based V2V communication to which thepresent invention may be applied.

Vehicular to Vehicular (V2V)

An E-UTRAN enables adjacent UEs to exchange V2V-related informationusing the E-UTRAN when a permission, grant and proximity criterion issatisfied. A proximity criterion may be configured to a worker.

Furthermore, a UE supporting the V2V application broadcasts applicationlayer information (e.g., as part of V2V service, regarding acorresponding location, dynamic and attributes). V2V payload needs to beflexible in order to accommodate different information contents. Theinformation may be periodically broadcasted based on a configurationprovided by an operator.

Vehicle-to-Infrastructure (V2I) Application

A UE supporting the V2I application transmits a message, including V2Iapplication information, to an RSU or a local-related applicationserver. The RSU and/or local-related application server transmits amessage, including V2I application information, to one or more UEssupporting the V2I application.

A locally related application program server provides services to aspecific geographical area. The same or different application programsmay be provided because there are several application program serversproviding service to an overlap area.

Vehicle-to-Network (V2N) Application

A UE supporting the V2N application communicates with an applicationserver supporting the V2N application. Both communicate with each otherthrough an EPS.

Vehicle-to-Pedestrian (V2P) Application

The V2P applications expect adjacent UEs to exchange V2P applicationinformation. The 3GPP transmission of a message including V2Papplication information requires a UE to obtain valid subscription andpermission from a network operator. Transmission for a valid subscriberis provided regardless of whether a UE is served by an E-UTRAN.

A UE supporting a V2P application transmits a message including V2Papplication information. The V2P application information is expected tobe transmitted by a UE supporting the V2X application in a vehicle(warning against a pedestrian) or a UE supporting a V2X applicationrelated a vulnerable road user (e.g., warning against a vehicle).

The 3GPP transmission of a message including V2P application informationincludes direct transmission between UEs due to a restricted directcommunication range and/or transmission between UEs through aninfrastructure structure supporting V2X communication, such as an RSX orapplication server.

A major difference between the 3GPP transmission of a message includingV2P application information and the 3GPP transmission of a messageincluding V2V application information lies in the characteristics of aUE. A UE supporting a V2P application used by a pedestrian may have alower battery capacity, for example, and may have limited radiosensitivity due to the antenna design. Accordingly, the UE cannottransmit a message having the same periodicity as a UE supporting theV2V application and/or also cannot receive a message.

Relative Priority of V2X Communication

Specific business core services (e.g., public safety, MPS) may berelatively given priority over the transmission of V2X applicationprogram information according to local/country regulation requirementsand an operator policy. The transmission of safety-related V2Xapplication information may have priority over the transmission of V2Xapplication program information not related to safety.

However, in general, an operator may control relative priority ofdifferent services.

Sidelink Communication-Related Identity (ID)

A sidelink communication and V2X sidelink communication-related ID towhich the present invention may be applied is described.

The following IDs are used for sidelink communication.

-   -   Source Layer-2 ID: identify the sender of data in sidelink        communication. Source Layer-2 ID is a 24-bit length and is used        with a Destination Layer-2 ID and LCID in order to identify an        RLC UM entity and PDCP entity on the receiver side.    -   Destination Layer-2 ID: identify the target of data in sidelink        communication and V2X sidelink communication. In the case of        sidelink communication, the destination layer -2 ID is a 24-bit        length and is split into two bit streams in the MAC layer.    -   One bit string is the LSB part (8 bits) of a target layer 2 ID        and delivered to a physical layer as a group target ID. This is        used to identify the target of intended data in sidelink control        information and to filter a packet in the physical layer.    -   The second bit text string is the MSB part (16 bits) of a target        layer 2 ID and delivered within a MAC header. This is used to        filter a packet in the MAC layer.    -   In the case of V2X sidelink communication, a Destination Layer-2        ID is not split and carried within a MAC header.

No Access Stratum signaling is necessary to form a group and toconfigure the Source Layer-2 ID, Destination Layer-2 ID and GroupDestination ID of a UE.

Such an ID is provided by a higher layer and derived from an ID providedby a higher layer. In the case of group cast and broadcast, a ProSe UEID provided by a higher layer is directly used as a Source layer-2 ID,and a ProSe Layer 2 group ID provided by a higher layer is directly usedas a Destination layer-2 ID in the MAC layer.

In the case of one-to-one communication, a ProSe UE ID and V2X sidelinkcommunication provided by a higher layer are directly used as a Sourcelayer-2 ID or Destination layer-2 ID in the MAC layer.

V2X sidelink communication is described more specifically.

The support of V2X service through the PC5 interface is provided by V2Xsidelink communication, that is, a communication mode in which a UE canperform direct communication through the PC5 interface. Thecommunication mode is supported when a UE is served by an E-UTRAN andwhen a UE is out-of-E-UTRA coverage.

Only a UE permitted to be used in V2X service may perform V2X sidelinkcommunication. Furthermore, in the case of V2X sidelink communication:

-   -   A sidelink transport channel (STCH) for sidelink communication        is also used for V2X sidelink communication.    -   V2X data transmitted in a resource configured for V2X sidelink        communication is not multi-transmitted along with non-V2X (e.g.,        public safety) data.

For sidelink communication, a control plane protocol stack for an SBCCHis also used for V2X sidelink communication as shown in FIG. 5 b.

A UE supporting V2X sidelink communication may operate in the two modesfor resource allocation:

-   -   Reserved resource allocation.    -   A UE needs to be in RRC_CONNECTED in order to transmit data.    -   A UE requests a transmission resource from an eNB. The eNB        schedules a transmission resource for the transmission of        sidelink control information and data.    -   UE autonomous resource selection.    -   A UE autonomously selects a resource in a resource pool and        performs transmission format selection for transmitting sidelink        control information and data.    -   When mapping between a zone and a V2X sidelink transmission        resource pool is configured, a UE selects a V2X sidelink        resource pool based on the zone where the UE is located.    -   A UE performs sensing for the (re)selection of sidelink        resources. Based on the results of the sensing, the UE        (re)selects some specific sidelink resources and reserves a        plurality of sidelink resources.

A maximum of two parallel independent resource reservation processes arepermitted to be performed by a UE. The UE is also permitted to performsingle resource selection for V2X sidelink transmission.

A geographical area may be configured by an eNB or may bepre-configured. When the area is configured, the world is divided intogeographical areas using a single fixing reference point (i.e.,geographical coordinates (0, 0)), length and width).

A UE determines a zone identity based on the length and width of eachzone, the number of zones in the length, and the number of zones in thewidth, and modulo operation using single fixing reference point.

The length and width of each zone, the number of zones in the length,and the number of zones in the width are provided by an eNB when a UE isin coverage and is pre-configured when the UE is out of coverage.

This area may be configured both in a service area and service area.

When a UE uses UE-autonomous resource selection with respect to the UEin coverage, an eNB may provide mapping between the V2X sidelinktransmission resource pools between a zone(s) and an SIB21.

With respect to UEs out of coverage, mapping between a zone(s) and V2Xsidelink transmission resource pools may be pre-configured.

If mapping between a zone(s) and a V2X sidelink transmission resourcepool is (pre)configured, a UE selects a transmission sidelink resourcein a resource pool corresponding to a zone where the UE is located.

The zone concept is not applied to a reception pool in addition to anexceptional V2X sidelink transmission pool.

A resource pool for V2X sidelink communication is not configured basedon priority.

For V2X sidelink transmission, during handover, a transmission resourcepool configuration including an exceptional transmission resource poolfor a target cell may be signaled in a handover command in order toreduce a transmission stop.

Accordingly, a UE may use the transmission sidelink resource pools ofthe target cell before handover is completed as long as synchronizationwith the target cell is performed.

If an exceptional transmission resource pool is included in a handovercommand, the UE randomly starts to use a selected resource in theexceptional transmission resource pool starting from the reception ofthe handover command. When resource allocation scheduled in the handovercommand is configured in the UE, the UE continues to use the exceptionaltransmission resource pool while a timer related to handover isexecuted. When autonomous resource selection is configured in the UE ina target cell, the UE continues to use the exceptional transmissionresource pool until initial sensing is completed in a transmissionresource pool for autonomous resource selection.

In an exceptional case (e.g., in a radio link failure (RLF), duringtransition from RRC IDLE to RRC CONNECTED or during a change in thededicated sidelink resource pool of a cell), a UE may select resourcesin an exceptional pool provided by the SIB 21 of a serving cell based onsensing and may temporarily use them.

In obtaining a reception pool broadcasted by a target cell, in order toavoid a stop time when a V2X message is received due to latency, asynchronization configuration and reception resource pool configurationfor the target cell may be signaled in a handover command with respectto RRC_CONNECTED UEs.

In the case of an RRC_IDLE UE, to minimize a sidelinktransmission/reception stop time related to the acquisition of the SIB21of a target cell depends on a UE implementation.

When a UE detects a cell on a corresponding carrier based on acriterion, the carrier is considered to be in-coverage in a carrier usedfor V2X sidelink communication.

If a UE permitted for V2X sidelink communication is in coverage for V2Xsidelink communication, it may use resource allocation scheduled basedon an eNB configuration or UE autonomous resource selection.

When a UE is out of coverage for V2X sidelink communication, atransmission and reception resource pool set for data is pre-configuredin the UE. A V2X sidelink communication resource is not shared withanother non-V2X application program transmitted through a sidelink.

If an RRC_CONNECTED UE is interested in V2X communication transmissionin order to request a sidelink resource, it may transmit a sidelink UEinformation message to a serving cell.

In order to receive V2X communication, when a UE is configured by ahigher layer and provided with a PC5 resource, the UE receives aconfigured resource.

A serving cell may provide a synchronization configuration for a carrierused for V2X sidelink communication. In this case, a UE follows asynchronization configuration received from a serving cell.

If a cell is not detected on the carrier used for V2X sidelinkcommunication and the UE does not receive the synchronizationconfiguration from the serving cell, the UE follows a pre-configuredsynchronization configuration. A synchronization criterion includesthree types of an eNB, a UE and a GNSS. If the GNSS is configured as asynchronization source, the UE uses UTC time in order to calculate adirect frame number and subframe number.

If eNB timing is set as a synchronization criterion for a UE for adedicated carrier for V2X, the UE follows a PCell(RRC_CONNECTED)/serving cell (RRC_IDLE) for synchronization and DLmeasurement.

PC5 Interface-Based V2X Operation Mode

FIG. 14 illustrates examples of a V2X operation mode based on a PC5interface only.

Referring to FIG. 14, a UE transmits a V2X message to a plurality of UEsin the area where a sidelink is supported. In this case, the V2X messagemeans a message mutually transmitted by a network entity or UE using aV2X sidelink communication system.

FIG. 14(a) means a V2V operation mode, FIG. 14(b) means a V2I operationmode, and FIG. 14(c) means a V2P operation mode. In this case, in thecase of V2I, one of a transmitter UE or a receiver UE is an RSU of a UEtype. Furthermore, in the case of V2P, one of a transmitter UE or areceiver UE is a pedestrian UE.

Uu Interface-Based V2X Operation Mode

FIG. 15 illustrates examples of a V2X operation mode based on a Uuinterface only.

Referring to FIG. 15, FIG. 15(a) means a V2V operation mode, FIG. 15(b)means a V2I operation mode, FIG. 15(c) means a V2P operation mode, andFIG. 15(d) means a V2N operation mode.

In this case, there is a mode in which a UE(s) transmits (uplinktransmission) a message (e.g., V2X message, V2I message) to a specificnetwork entity (e.g., eNB, E-UTRAN) and a specific network entitytransmits (downlink transmission) a message (e.g., V2X message, I2Vmessage) to a plurality of UEs located in a specific area.

In this case, the specific network entity may be an eNB, an E-UTRAN oran RSU of an eNB type.

Furthermore, the UE may communicate with an application server.

Furthermore, in order to support a Uu interface-based V2X operationmode, an E-UTRAN performs the uplink reception and downlink transmissionof V2X messages. For the downlink, the E-UTRAN may use a broadcastmechanism.

Uu Interface and PC5 Interface-Based V2X Operation Mode

FIG. 16 illustrates examples of a V2X operation mode based on both theUu interface and the PC5 interface.

Referring to FIG. 16, FIG. 16(a) means a scenario 3A mode in which anE-UTRAN receives a V2X message from a UE type RSU and transmits thereceived V2X message to a plurality of UEs. In contrast, FIG. 16(b)means a scenario 3B mode in which a UE transmits a V2X message to anE-UTRAN, the E-UTRAN transmits the received V2X message to one or moreUE type RSUs, and a UE type RSU transmits a V2X message to other UEsthrough a sidelink.

More specifically, if both the Uu interface and the PC5 interface areused, an RSU (e.g., an RSU of a UE type) is present between UEs and aspecific network entity. The RSU may receive a message from the UEs ortransmits a message to the UEs.

In this case, it is assumed that the RSU is connected to a specificnetwork entity.

The specific network entity may receive a message from the UEs using theRSU or may transmit a message to the UEs. In this case, the specificnetwork entity may be an eNB, an E-UTRAN or an RSU of an eNB type.

In this case, a specific network entity or RSU that receives the messageof the UEs may operate through the Uu interface (e.g., Uuvehicle-to-infrastructure (V2I)) using a legacy LTE uplink method.

Alternatively, the specific network entity or the RSU may operatethrough the PC5 interface (e.g., PC5 V2I or PC5 V2V signal overhearing)using a separate resource or separate band supporting communicationbetween UEs.

Likewise, the specific network entity or RSU transmitting a message tothe UEs may operate through the Uu interface or the PC5 interface usinga legacy LTE downlink method.

(2) Scheduling Scheme in V2V Sidelink Communication

In the case of V2V sidelink communication, an eNB indication-basedscheduling method (i.e., Mode 1) of sidelink communication and ascheduling method (i.e., Mode 2) for a UE to autonomously select aresource within a specific resource pool may be used.

However, in V2V sidelink communication, Mode 3 corresponding to Mode 1and Mode 4 corresponding to Mode 2 are defined so that they aredifferent from those in the case of the existing sidelink communication.

In this case, Mode 3 may be referred to as a distributed schedulingmethod, and Mode 4 may be referred to as an eNB scheduling method.

In particular, sensing based on a semi-persistent transmission-basedmechanism may be defined with respect to the distributed schedulingmethod (i.e., Mode 4). Most of V2V traffic from a UE is periodical. TheV2V traffic is used to sense congestion for a resource and to estimate afuture congestion for a corresponding resource. Corresponding resourcesare booked based on the estimation. The use of a channel can beoptimized by improving separation efficiency between transmitters usingan overlap resource through such a technology.

A configuration 1 for Mode 4 (i.e., distributed scheduling) and aconfiguration 2 for Mode 3 (i.e., eNB scheduling) may be representedlike FIG. 17.

FIG. 17 illustrates examples of scheduling methods which may be appliedto V2V sidelink communication.

Referring to FIG. 17, two configurations use a V2V communicationdedicated carrier. That is, a band for the dedicated carrier is used foronly PC5-based V2V communication. In this case, FIG. 17(a) illustrates amethod for the configuration 1, and FIG. 17(b) illustrates a method forthe configuration 2.

In this case, in both cases, time synchronization may be performed by aglobal navigation satellite system (GNSS).

FIG. 17(a), that is, in the case of the configuration 1, the schedulingand interference management of V2V traffic is supported based on adistributed algorithm (i.e., Mode 4) implemented between vehicles. Asdescribed above, the distributed algorithm is based on sensing throughsemi-persistent transmission. Furthermore, a mechanism in which resourceallocation depends on geographical information is defined.

In contrast, FIG. 17(b), that is, in the case of the configuration 2,the scheduling and interference management of V2V traffic is supportedby an eNB through control signaling through the Uu interface. The eNBallocates resources used for V2V signaling in a dynamic manner.

As described above, in order to perform direct communication between UEsthrough Sidelink and the like, an eNB may select and indicate a resourceto transmit a message, and signal the related control message and thelike for the UE. As such, the scheme that an eNB indicates and signalsmay be referred to as network-assisted scheme and/or mode 1 scheme.Different from this, the scheme that a UE directly selects a resourcemay be referred to as UE-autonomous scheme and/or mode 2 scheme. Inaddition, in the case of the V2X Sidelink communication, the mode 1scheme may be referred to as mode 3 scheme and the mode 2 scheme may bereferred to as mode 4 scheme.

When a communication is performed between UEs, the UE needs to transmitScheduling Assignment (SA) that designates resource allocationinformation and the like for transmission data in Sidelink resourceselection and scheduling to another UE. In addition, in the case of themode 1 scheme, an eNB transmits Downlink Control Information (DCI) thatdesignates information for SA and information for transmission data to aUE. Here, the DCI may include a part of information for SA transmissionand contents of SA (i.e., information related to data transmission).Furthermore, the DCI may be referred to as Sidelink grant, and the SAmay be referred to as Sidelink Control Information (SCI).

At this time, pattern for transmitting SA and/or data (e.g.,time/frequency resource pattern) and/or information for schedulingscheme and the like may be added as a specific field of the DCI. In thiscase, a part of the DCI format designed with the same size as theexisting DCI format (i.e., DCI format 0) may be changed. For example,when SA and/or data is retransmitted, in the case that an eNB transmitsonly DCI for an initial transmission, not transmitting DCI in eachretransmission (or transmission), the eNB needs to inform theinformation for remaining SA and/or data. Here, the transmission of onlythe DCI for the initial transmission may be designed for reducing DCIoverhead.

As described above, while an addition of specific field(s) for DCI isconsidered, in the case that the fields for the parameters previouslyexisted are maintained without any change, a length (i.e., size) of DCIis increased. In this case, as a size changes for each DCI format, aproblem may occur that count and/or type of blind decoding performed ina UE is changed. That is, in the case that a size of DCI format is notregularly configured for each format, overhead of blind decoding of UEmay be increased.

Accordingly, a method of maintaining a size of DCI format (i.e., thesize is configured as the same as DCI format 0) needs to be consideredeven in the case that new fields are added in DCI. In this case, amethod of adding new fields may be considered while a part of existingfields in the existing DCI is deleted or constricted.

At this time, the value indicated in the corresponding field (i.e.,deleted or constricted field) may be indicated to a UE by using othersignaling or other field which may be replaced. Here, the other fieldwhich may be replaced may mean a newly added field as well as theexisting fields in the existing DCI.

Hereinafter, in the present disclosure, a method for configuring a DCIformat used for V2X Sidelink communication will be described in detail.

As described above, the DCI is information used for scheduling SA (orSCI or PSCCH), and the SA is information used for scheduling (Sidelink)data (or PSSCH).

In addition, in the case of the Sidelink communication, the DCI formatthat an eNB transmits to a transmission UE may be represented as DCIformat 5, and the SA that a transmission UE transmits to a reception UEmay be represented as SCI format.

Particularly, in the case of the V2X Sidelink communication, the DCIformat that an eNB transmits to a transmission UE may be represented asDCI format 5A, and the SA that a transmission UE transmits to areception UE may be represented as SCI format 1. However, this is justan example, but not limited to the representation, and may berepresented in various forms. For example, the DCI format used for theV2X Sidelink communication may be represented as DCI format 5, DCIformat 5A, modified DCI format 5 or new DCI format 5, and the like.

In addition, hereinafter, the description described in relation to thepresent invention may also be extendedly applied to other wirelesscommunication operates in the same way as well as the V2X Sidelinkcommunication.

In this case, as described above, even in the case that additionalinformation (i.e., additional field), which was not existed in the DCIformat, is included, the methods for maintaining a length (i.e., size)of the DCI format as the same as the existing case are described in thepresent disclosure.

Furthermore, the methods described in the present disclosure may beapplied as a method for reducing a size of the general DCI format aswell as a method for maintaining a size of the DCI format which is usedfor the V2X Sidelink communication. The reducing of a size of the DCIformat itself may mean that an amount of resource (e.g., radio resource,power, transmission time, etc.) consumed for transmitting the DCI isreduced. Accordingly, when a size of the DCI format is reduced, an eNBmay perform scheduling more efficiently in an aspect of resource.

In addition, the embodiments described below are distinguished for theconvenience of description, but a part of the configuration of any oneembodiment may be included in the other embodiment, or may be replacedby the configuration or the characteristics corresponding to the otherembodiment.

Method for reducing a size of a field related to SA and/or resource ofdata

In order to maintain a size of DCI while a new field is added to theDCI, a method for reducing a size of the SA resource field (i.e.,resource field for Physical Sidelink Control Channel (PSCCH)) includedin the existing DCI may be considered.

In comparison with the existing case (e.g., Sidelink communicationbetween normal UEs), the number of resources usable for V2Xcommunication or SA transmission in V2V communication may not be changedor only a few of it may be changed. In this case, there is littlepossibility that a size (e.g., 6 bits) of the field indicating the SAresource defined in the existing DCI format (e.g., DCI format 5/5A) withthe change of the scheme of multiplexing SA and/or data (e.g., FrequencyDivision Multiplexing (FDM) scheme and Time Division Multiplexing (TDM)scheme) only.

However, in the case that a UE may know a part or the whole ofallocation information for time/frequency resource of SA transmission,may be indicated with the information from an eNB and the like, or mayestimate it autonomously, the size of the field indicating the SAresource may be reduced. That is, a method of reducing the fieldindicating the SA field using predefined information (i.e., advanceinformation) or implicit information (configuring the size of the fieldindicating the SA resource to smaller than 6 bits).

For example, in the case that it is configured that SA is transmittedafter a specific time offset (or timing gap, subframe offset) based on atransmission position of DCI, the information for the time resource ofSA transmission is not required to be included in the DCI. As anexample, in the case that the DCI is transmitted in subframe #n, it maybe configured that SA is transmitted in subframe #n+k.

Here, the configuration information for the specific timing offset maybe predefined (predetermined or preconfigured) on a system or an eNB mayinform the configuration information through signaling (e.g., higherlayer signaling) to a UE. As an example, this method may be performed asshown in FIG. 18.

FIG. 18 illustrates an example of SA transmission scheme. FIG. 18 isshown just for the convenience of description, but does not limit thescope of the present invention.

Referring to FIG. 18, each of the squares depicted means a subframe, andthe case is assumed that SA is transmitted in 4th subframe after DCItransmission. Particularly, in the case that the DCI is transmitted insubframe #n 1802, it may be configured that SA is transmitted insubframe #n+4 1804. Alternatively, different from FIG. 18, it may beconfigured that SA is transmitted in the first Sidelink subframe existed(or generated) after subframe #n+4 1804.

As described above, in the case that the SA transmission is configuredto be transmitted after a specific timing offset (or timing gap) basedon a transmission position of the DCI, the eNB may indicate onlyfrequency resource allocation information of the SA transmission to theUE using the DCI. In addition, in the case that the SA transmission isconfigured to be performed at a position departed from as much as aspecific timing offset and/or a specific frequency offset based on atransmission position of the DCI, the eNB may transmit the DCI in whichtime resource allocation information and/or frequency resourceallocation information are/is excluded to the UE. In other words, sincea part of resource allocation information may be excluded from the DCIbased on time/frequency relationship between the DCI transmission andthe SA transmission, a size of the field indicating the SA resource maybe reduced in comparison with the existing DCI.

Alternatively, in the case that SA and data are multiplexed in the FDMscheme and/or SA is transmitted in a sub-channel unit including aregular number of resource blocks (RBs), a size of the frequencyresource allocation information of the SA transmission may be reduced.

In addition, the method described above may reduce the size of the fieldindicating the SA resource, and may also be efficiently applied to thecase that V2X communication or V2V communication uses wide band onfrequency (i.e., supports wide bandwidth). Particularly, uncertainty ofSA detection may be reduced as specific time/frequency offset is usedbetween the DCI transmission and the SA transmission, and accordingly,an efficient SA scheduling may be performed in the FDM scheme.

Further, in relation to the resource information included in the DCI, amethod of reducing a size of RB assignment filed as well as the SAresource field may be considered. The RB assignment filed included inthe existing DCI field is configured to distinguish the cases of allcombinations between the timing when the RB assignment is started andthe timing (or the number of assigned RBs) when the RB assignment isended.

At this time, in the case that a UE may estimate (or infer) the numberof RBs assigned by signaling, indication or other field included in theDCI from an eNB and the like, the size of the RB assignment field may bereduced. Alternatively, even in the case that a UE may know a startingpoint of the RB assignment through interrelationship between frequencyassignment schemes of SA and data, the size of the RB assignment fieldmay be reduced. In this case, the number of RBs (i.e., RB size) may bepredefined depending on types of V2V or V2X message which is used forthe data transmission. In addition, in the case that a resourceallocation unit for data is transmitted in a sub-channel unit includinga regular number of RBs, the size (i.e., bit number) of the RBassignment field may be changed as the resource allocation unit ischanged.

Method for Indicating Modulation and Coding Scheme (MCS) Index

For the mode 1 scheme described above, Semi-Persistent Scheduling (SPS)as well as dynamic scheduling may be considered for data transmissionbetween UEs. In this case, a common (or single) DCI (or DCI format) maybe configured, which may be applied to both of the two (or more) typesof scheduling scheme. Separate DCIs may be configured for eachscheduling scheme, but in order to reduce complexity of DCI (i.e., inorder to reduce blind decoding count and/or types of UE), the common DCImay be used for the scheduling schemes. The common DCI may also bereferred to as mode 1 Sidelink DCI or mode 1 Sidelink grant.

At this time, in the case of the dynamic scheduling scheme, informationof specific DCI is used once or for transmissions of associated data (oronly for a specific transmission period). Different from this, in thecase of the SPS scheme, information of specific DCI may be used untilthe corresponding SPS transmission operation is released. Accordingly,in order to common DCI for two types of scheduling scheme, a fieldindicating a valid period of the corresponding DCI may be additionallyincluded. Here, the field indicating a valid period of the correspondingDCI may mean a field that distinguishes how long period thecorresponding DCI is valid. For example, the field indicating a validperiod of the corresponding DCI may include a field that distinguishesdynamic scheduling from SPS.

In the case that dynamic transmission and SPS transmission aredistinguished using the field, a specific field may be configured inaccordance of each of the uses for the dynamic transmission and the SPStransmission. In this case, a UE may interpret (or use) thecorresponding specific field according to each of the uses for thedynamic transmission and the SPS transmission. Alternatively, a part orthe whole of the remaining fields except the field that distinguishesthe dynamic scheduling and the SPS may be differently configured (ordefined) for the dynamic transmission and the SPS transmission.

For example, in the case that the field that distinguishes the dynamicscheduling and the SPS is configured as 1 bit, 0 may indicate that thecorresponding DCI is for the dynamic scheduling. That is, 0 may indicatethe DCI defined only for one-shot transmission or the associatedtransmission (or retransmission). Different from this, 1 may indicatethat the corresponding DCI is for the SPS. Accordingly, when a UEreceives the DCI configured as 1, the corresponding UE may operate basedon the SPS transmission. That is, the UE may transmit SA and/or dataindicated by the corresponding DCI during the previously configuredand/or a predetermined period indicated by signaling (e.g., RRCsignaling), and the like or until the corresponding SPS transmissionoperation is released.

In relation to the predetermined period, the UE may count the number ofSA and/or data being transmitted and perform a transmission of SA and/ordata until a corresponding timer expires. Alternatively, the UE maycount time lapsed from the timing when the DCI is transmitted andperform a transmission of SA and/or data until a corresponding timerexpires.

As described above, in the case that the SPS transmission as well as thedynamic transmission is scheduled using a common DCI (i.e., the same DCIformat), various types of messages may be transmitted in the aspect of asize of message block, a size of transport block, and the like.Accordingly, an eNB is required to designate the Modulation and CodingScheme (MCS) applied to the various types of messages.

In this case, the eNB may indicate an MCS index in semi-static mannerfor a UE through higher layer signaling (e.g., RRC signaling) and thelike.

Alternatively, the MCS index is included in the existing SA (i.e., SCIformat), but a method of including a field indicating information forthe MCS in the DCI may be considered so as to a UE may detect MCS leveleven in the case that the UE fails to receive the SA. Particularly, inthe case that the DCI includes a field indicating information for theMCS, even in the case that the UE performing SPS transmission fails toreceive the SA, the UE may detect a change of the MCS using the DCI.

For example, like DCI format 0, a field indicating the MCS (i.e., MCSindex) or MCS and redundancy version may be included in the DCI which isused for Sidelink (or V2X, V2V) communication. At this time, thecorresponding field may be configured with 5 bits considering the usableMCS level.

For another example, by using the characteristics that transmittabletypes of message is limited for Sidelink (or V2X, V2V) communication, amethod of reducing a size of the field indicating the MCS index may beused (i.e., configuring a size of the field indicating the MCS index tobe smaller than 5 bits). In the case of using the field of which size isreduced, an eNB may indicate the MCS index for a transmission of themessage related to the corresponding DCI to a UE by using the remainingbits which are occurred owing to the reduction of size of other fieldsincluded in the DCI. That is, in the case of using the method, there isan advantage that a size of the existing DCI may be maintained even inthe case that the remaining bit is configured smaller.

Particularly, the eNB may transmit the DCI including an additional fieldindicating the MCS index and the like to the UE. In other words, the DCImay include a separate field indicating a specific message among themessages which are categorized according to the MCS index, a size ofmessage, and the like. Here, the specific message may mean a set ofspecific messages which are selected among preconfigured multiplemessage sets.

In the case of the dynamic scheduling transmission, various types ofmessages may be transmitted in comparison with the SPS transmission.However, such V2V and/or V2X message transmission is performed inbroadcast manner mainly, not a transmission to a specific UE. Therefore,the types of messages transmitted in the V2V and/or V2X communication(or Sidelink communication) may be limited. Accordingly, a method may beused that an eNB indicates only a part of MCSs corresponding to thelimited types of messages. In addition, based on the characteristics ofperforming repeated transmission of the SPS transmission, when the MCSsatisfying a predetermined level, a message transmission may be smoothlyperformed. Accordingly, in the case of the SPS transmission, even in thecase that a specific MCS is indicated among a part of MCSs proper forthe SPS transmission, not the whole MCSs, a message transmission may beperformed without any problem.

As described above, in the case of the V2V and/or V2X communication (orSidelink communication), only a part of the MCS indexes may beselectively used among the usable MCS indexes for a messagetransmission, and only a part of the whole transport block sizes may beselectively used. Furthermore, when sizes of the MCS index and thetransport block used for the message transmission are determined, a sizeof resource block (RB) to be used for the message transmission may alsobe determined. Alternatively, the MCS index may be determined after thesize of resource block and the size of transport block are determined,and any combinations of the order of determining thereof are available.

As such, the MCS (i.e., MCS index) required for a type of transmittedmessage, a size of transport block (TB size), a size of resource block(RB size), and the like may be predefined, and made up as a set. Thatis, according to the MCS required for a type of message used in the V2Vand/or V2X communication, a size of transport block, a size of resourceblock, and the like, one or more message sets may be predefined (orpreconfigured or predetermined). In this case, even in the case that aUE detects a set of messages indicated by the corresponding DCI, the UEmay obtain the information for the MCS level required for a transmissionof the corresponding message, a size of transport block and a size ofresource block.

In addition, in the case that a coding rate (i.e., coderate) of thecorresponding message is not sufficient or the corresponding message hasan importance to be transmitted repeatedly, the corresponding message isconfigured to be transmitted repeatedly. In this case, the informationfor the (maximum) retransmission count, the coding rate, and the likemay be additionally included in addition to the MCS (i.e., MCS index), asize of transport block, a size of resource block, and the like.

As an example, the message sets may be configured as represented inTable 3 below.

TABLE 3 Message Message Set size N_rpt N_PRB I_TBS I_MCS Q_m Coderate 1190 Byte 3 10 9 (1544 bit) 9 2 0.268 2 300 Byte 2 10 13 (2536 bit) 14 40.330 3 800 Byte 2 25 13 (6456 bit) 14 4 0.336 4 1600 Byte 2 50 13(12960 bit) 14 4 0.338 . . . . . . . . . . . . . . . . . . . . .

In Table 3, ‘Message size’ means a size of the corresponding message,‘N_rpt’ means a number of repetition transmissions of the correspondingmessage, ‘N_PRB’ means the number of resource block (i.e., a size ofresource block) used for transmitting the corresponding message, ‘I_TBS’means an index (size) of the transport block used for transmitting thecorresponding message, ‘I_MCS’ means an MCS index used for transmittingthe corresponding message, ‘Q_m” means a modulation order used fortransmitting the corresponding message, and ‘coderate’ means a code rateof the corresponding message.

At this time, as represented in Table 3, in the case that 4 types ofmessage sets (i.e., a first message set (Message set 1), a secondmessage set (Message set 2), a third message set (Message set 3) and afourth message set (Message 4)) are configured, a message set fieldconfigured with a combination of a size of message, a number ofrepetition transmissions, the number of resource block, and the like maybe configured with 2 bits. Here, the message set field may mean aseparate field indicating the MCS index, and the like included in theDCI. At this time, in the case that the message set field is configuredwith 2 bits, the first message set is indicated by ‘00’, the secondmessage set is indicated by ‘01’, the third message set is indicated by‘10’ and the fourth message set is indicated by ‘11’. That is, the MCSindex used for transmitting the corresponding message may be indicatedby using 2 bits only which is decreased by 3 bits in comparison with theexisting 5 bits.

In this case, the configuration information for the message setdescribed above may be predefined on a system, or the configurationinformation for the message set may be transmitted to a UE throughhigher layer signaling, and the like. In addition, the configurationinformation for the message set may be configured with a combination ofvarious parameters related to the corresponding message types as well asa size of message, a number of repetition transmissions, the number ofresource block, and the like.

Further, in the various embodiments, the retransmission count (e.g.,N_rpt) used for V2V and/or V2X communication may be indicated byTime-Resource Pattern of Transmission (T-RPT) field and so on includedin a new field indicating the message set or the existing DCI (e.g., DCIformat 5). In addition, in the case that the new field and the T-RPTfield are not used, the retransmission count may be indicated throughhigher layer signaling (e.g., RRC signaling), or a separate fieldindicating the retransmission count may be included in the DCI.

FIG. 19 illustrates an operation flowchart for a first UE to transmitand receive data in a wireless communication system supportingVehicle-to-Everything (V2X). FIG. 19 is shown just for the convenienceof description, but not intended to limit the scope of the presentinvention.

Referring to FIG. 19, the case is assumed that a first UE receive aresource selection and an indication for scheduling through downlinkcontrol information from an eNB in order to perform Sidelinkcommunication (i.e., Device-to-Device communication) with a second UE.

In step S1905, the first UE receives downlink control information (DCI)including resource allocation information related to a transmission ofcontrol information (e.g., SA) with respect to Sidelink from the eNB. Atthis time, the corresponding resource allocation information may meanthe SA resource allocation information of which size is adjusted (i.e.,the bit number is configured smaller than the SA resource allocationinformation included in the existing DCI) described above.

After the first UE receives the DCI, in step S1910, the first UE maytransmit Sidelink control information and at least one data (i.e., datatransmitted through Sidelink, Sidelink data) to the second UE. In thiscase, the transmission of the at least one data may be performed afterthe transmission of control information with respect to Sidelink orperformed simultaneously.

At this time, the transmission of control information with respect toSidelink is performed in a second subframe located after a preconfiguredoffset from a first subframe in which the DCI is received. Here, thepreconfigured offset may mean a specific timing offset described in thefirst embodiment described above. That is, the preconfigured offset maybe configured based on the relationship between a reception position ofthe DCI (or DCI transmission position in the aspect of an eNB) and atransmission position of the control information with respect toSidelink. In addition, the second subframe may include a first Sidelinksubframe located after a preconfigured offset from the first subframe.That is, the first subframe is subframe #n, the second subframe mayinclude subframe #n+4 (e.g., n+4th subframe) or a first (or initial)subframe generated after the subframe #n+4.

In this case, the resource allocation information included in the DCImay include resource allocation information of which size is adjustedbased on at least one of the preconfigured offset or a transmission unit(e.g., sub-channel unit including a preconfigured (i.e., predetermined)number of RBs) on the frequency domain related to the transmission ofcontrol information with respect to the Sidelink. For example, theresource allocation information included in the DCI may mean resourceallocation information of which size is adjusted (e.g., configured witha bit number smaller than 6 bits) as the time resource allocationinformation is excluded according to the preconfigured offset. At thistime, the bit number configuring the DCI format related to the DCI maybe configured as the same bit number configuring other DCI format (e.g.,DCI format 0). That is, a length of the DCI format may be identicallyconfigured with the length of DCI format 0.

In addition, the DCI may further include specific information (i.e.,specific field) indicating an MCS index for the at least one datatransmission. For example, a separate field indicating the MCS describedin the second embodiment above in the DCI may be additionally included.

In this case, the specific information may include informationindicating a specific message set among preconfigured message sets.Here, the preconfigured message sets may mean the message sets describedin the second embodiment above. In other words, the preconfiguredmessage sets may be configured based on at least one of an MCS indexrequired related to a transmission of at least one data, the number oftransport blocks, or the number of resource blocks. At this time, thespecific information may be configured with a bit number smaller than 5bits, and the bit number configuring the DCI format related to the DCImay be identically configured with the bit number configuring other DCIformat (e.g., DCI format 0).

Further, the DCI may further include control information with respect tothe Sidelink and information indicating whether the transmission of atleast one data is performed according to the SPS scheme (e.g., a fieldindicating a valid period of the corresponding DCI in the secondembodiment).

According to the methods described above, the size of the DCI (e.g.,mode 1 sidelink grant) used in V2V and/or V2X communication may beidentically configured with the size of the existing other DCI (e.g.,DCI format 0). Accordingly, even in the case that additional informationrequired for V2V and/or V2X communication is included in the DCI, a UEmay perform the blind decoding for the DCI, which was performed for theexisting DCI, in the same manner. That is, even in the case thatadditional information required for V2V and/or V2X communication isincluded in the DCI, a UE is not required to perform additional blinddecoding in comparison with the previous case, and there is an advantagethat DCI overhead does not occur.

Hereinafter, a method for determining transmission timing for SAtransmission and data transmission in V2X Sidelink communicationproposed in the present disclosure is described in detail with referenceto the related drawing.

As described above, (1) DCI is information used for scheduling SA (orSCI or PSCCH) and (2) SA is information used for scheduling (Sidelink)data (or PSSCH), defined in Sidelink communication.

In addition, in the case of Sidelink communication, the DCI formattransmitted to a transmission UE from an eNB may be represented as DCIformat 5, and the SA transmitted to a reception UE from a transmissionUE may be represented as Sidelink Control Information (SCI) format.

Particularly, in the case of V2X Sidelink communication, the DCI formattransmitted to a transmission UE from an eNB may be represented as DCIformat 5A, and the SA transmitted to a reception UE from a transmissionUE may be represented as Sidelink Control Information (SCI) format 1.

However, this is just an example, and not limited to the representation,but may be represented as various forms.

Hereinafter, the description described in relation to the presentinvention may also be extendedly applied to other wireless communicationoperates in the same way as well as the V2X Sidelink communication.

First, the method proposed in the present disclosure in V2X Sidelinkcommunication may be classified into a first embodiment and a secondembodiment largely according to a use (or transmission) of T-RPT field,and the first embodiment and the second embodiment may be appliedtogether as occasion demands.

The DCI format used for V2X Sidelink communication includes a part ofcontents of the SA.

Here, the DCI format may be represented as DCI format 5 or DCI format5A, or modified DCI format 5 or new DCI format 5, and the like.

A part of the contents of the SA included in the DCI format may includea field indicating T-RPT index that represents a pattern for a repeatedtransmission or a retransmission of data.

Here, the term, ‘pattern’ may be interpreted as the same meaning as aregular form or a specific form, and the like.

Particularly, in the DCI used in Mode 1 Sidelink communication, it maybe classified into the first embodiment and the second embodiment asbelow according to use of the T-RPT field.

Mode 1 Sidelink, as described above, is a network-assisting scheme thatan eNB directly indicates or signals the Sidelink communication relatedinformation to a UE, and may also be represented as Mode 3 in V2XSidelink communication.

Embodiment 1: (Re)Use T-RPT Field

First, a first embodiment is in relation to a method for (re)using T-RPTfield included in the DCI of the existing Sidelink communication for V2XSidelink communication.

That is, in the case that the T-RPT field is used in V2X Sidelinkcommunication without any change, all of information for a repeatedtransmission of data may be indicated in single DCI (up to 4retransmissions).

In other words, for a repeated transmission of V2X Sidelinkcommunication of a transmission UE, an eNB transmits V2X sidelink DCIincluding T-RPT field to the transmission UE.

By using the T-RPT field, a transmission UE is able to (repeatedly)transmit a message or data to a reception UE on various timings, andflexibility of resource allocation may become significantly increased.

Particularly, in the case that the T-RPT field is used in the DCI of V2XSidelink communication, a part of resource collision, half-duplexproblem, and the like, which may occur by using different T-RPTs betweenUEs, may be solved.

Here, as a method of interpreting the T-RPT pattern and applying it toan actual data transmission, largely, (1) a method of applying the T-RPTpattern based on SA transmission timing (method 1) and (2) a method ofapplying the T-RPT pattern based on a predetermined offset from DCItransmission timing (method 2) may be considered.

(Method 1: Application of T-RPT Pattern Based on SA Transmission Timing)

FIG. 20 illustrates a method for determining a transmission timing ofdata using T-RPT pattern proposed in the present disclosure.

Particularly, FIG. 20a illustrates an example of a method fordetermining data transmission timing based on SA transmission timing.

That is, method 1 relates to a method of synchronizing a startingposition of data transmission according to T-RPT pattern with a startingposition of SA transmission, and the corresponding method provides amethod for solving the situation that a UE is unable to transmit datawhen the UE fails to obtain a starting position of data transmission inthe out-of coverage scenario.

For example, a case may occur that a UE operating mode 2 fails to obtainthe information related to data transmission starting point through SIB,RRC signaling or DCI from an eNB.

In this case, a problem may occur that the UE is unable to (re)transmitdata.

Accordingly, method 1 defines such that data transmission timing issynchronized with transmission timing of SA.

When applying method 1, it is assumed that the SA includes T-RPTpattern, and it is assumed that a UE operating in Mode 1 (or Mode 3)generates SA through DCI and a UE operating in Mode 2 (or Mode 4)obtains SA in advance or generates SA independently (if it is required).

Particularly, the situation in which method 1 is applied may be asbelow.

In the case that a first UE receiving information related to datatransmission starting point through SIB or RRC signaling, and the liketransmits SA to a second UE that fails to receive information related tothe data transmission starting point, the second UE interprets that theT-RPT pattern included in the SA is applied from the SA transmissiontiming.

That is, the first UE starts a transmission of data on a subframe whichis the same as the subframe for transmitting the SA to the second UE.

In addition, the second UE may assume that data is (re)transmittedaccording to the T-RPT pattern from the SA transmission timing.

Here, the first UE is a UE that is able to receive information relatedto the data transmission starting timing from an eNB, and may be a UEthat operates in Mode 1 (or Mode 3), and the second UE is a UE that isunable to receive information related to the data transmission startingtiming from an eNB, and may be a UE that operates in Mode 2 (or Mode 4).

And, it is assumed that the second UE may receive SIB or RRC signaling,but when applying method 1, the second UE is unable to receive SIB orRRC signaling including the information related to data transmissionstarting timing.

In addition, a single SA may schedule a single Transport Block (TB).

The contents related to method 1 described above may be identicallyapplied to method 2 (determining data transmission timing considering arelationship with DCI transmission timing) that will be described below.

For example, according to method 1, the DCI is transmitted in subframe(SF) #n, the SA is transmitted SF #(n+k) (e.g., k=4), and the T-RPTpattern indicated by the SA is applied from SF #(n+k) timing.

The T-RPT pattern indicated by the SA may be included in the DCI whichis transmitted on SF #n.

Referring to FIG. 20a , an eNB may transmit the DCI to a transmission UEon subframe (SF) #n 2001, and the transmission UE may transmit the SA toa reception UE on SF #(n+k) (e.g., k=4) 2002.

At this time, the transmission UE may transmit data related to the SA tothe reception UE by applying the T-RPT pattern indicated by the SA fromthe timing when the SA is transmitted, that is, SF #(n+k) timing.

It may be interpreted that the T-RPT pattern represents a specific formor a regular form of the time resource for a data transmission.

That is, the T-RPT pattern is a concept representing a form for aplurality of data resources, and a plurality of data resources mayinclude repeated data resource or retransmitted data resource.

For example, as shown in FIG. 20a , in the case that the T-RPT patternis ‘00101011’ (2003), an applying timing of data transmission is SF #n+4(2004) on which the SA is transmitted.

That is, the subframe on which data transmission is started is the sameas the subframe on which the SA is transmitted.

In addition, the timing when an actual data transmission occurs may beSF #(n+k+2)(2005), SF #(n+k+4)(2006), SF #(n+k+6)(2007) and SF#(n+k+7)(2008) as shown in FIG. 20 a.

In FIG. 20a , k is 4, and total (re)transmission count of data is 4times.

Next, a case of (re)transmitting data using a plurality of SAs isdescribed with reference to FIG. 20b and FIG. 20 c.

FIG. 20a shows the case that a transmission or a retransmission of alldata is performed after a single SA transmission.

Different from FIG. 20a , a plurality of SAs may be used for atransmission or a retransmission of all data.

That is, referring to FIG. 20b and FIG. 20c , it is shown that a part ofdata (re)transmission is performed after the first SA transmission, and(re)transmission for the remaining data is performed through the next SA(or the second SA) transmission.

In FIG. 20a and FIG. 20c , it is assumed that data is (re)transmittedtwice times per a single SA.

As shown in FIG. 20b , the second SA transmission timing transmittedafter the first SA transmission may be obtained from a timing gapbetween the first SA transmission timing and the first data transmissiontiming.

The timing gap may be represented as an offset, and the timing gap maybe defined in a subframe unit.

However, when the method shown in FIG. 20b is applied, before all of thefirst SA transmission 2010 and the data 2020 related to the first SAtransmission are transmitted, the second SA 2030 may be transmitted, andaccordingly, the case may occur that the data associated with the firstSA transmission and the second SA are (unintentionally) FDMed, or thedata associated with the first SA transmission is transmitted on thesame timing or the ahead timing of the second SA transmission timing.

Accordingly, in order to solve such a situation, a method oftransmitting the second SA may be considered on the timing immediatelynext to the timing (or subframe) when the last data (re)transmission iscompleted associated with the first SA or on the timing departing asmuch as a predetermined offset.

For example, FIG. 20c shows the case that two data 2012 (re)transmissionassociated with the first SA 2011 are completed, and the second SA 2013is transmitted on the timing departing as much as 0 TTI offset.

The size of the predetermined offset may be indicated through RRCsignaling, and the like, or predefined, or indicated through a physicalchannel (e.g., DCI).

Method 2: Application of T-RPT Pattern After a Predetermined Timing Gapfrom DCI Transmission Timing

Different from method 1, method 2 relates to a method for applying T-RPTpattern after a predetermined timing gap from the DCI transmissiontiming, not the SA transmission timing.

FIG. 21 illustrates another method for determining a transmission timingof data using T-RPT pattern proposed in the present disclosure.

As shown in FIG. 21a , an eNB transmits DCI to a transmission UE onsubframe (SF) #n, and the transmission UE transmits data to a receptionUE by applying the T-PRT pattern on SF #(n+m) (e.g., m=4).

Here, the m value may be indicated through RRC signaling, and the like,or predefined, or forwarded or transmitted to the UE through a DCI field(e.g. T-RPT offset field).

FIG. 21a shows the case that T-RPT pattern is ‘00101011’ and m=4.

In FIG. 21a , the timing gap k (k=5, 6, . . . ) between DCI and SAtransmission timings may be indicated to a UE through RRC signaling, orpredefined, or forwarded through a DCI field (e.g. T-RPT offset field).

Here, in the case that the m value corresponding to the T-RPT timing gapis identical to the k value defined in the method 1 described above,method 1 and method 2 operate in the same manner, that is, data is(re)transmitted on the same timing.

FIG. 21b illustrates another method for determining a transmissiontiming of data using T-RPT pattern proposed in the present disclosure.

Particularly, FIG. 21b shows the case that data is transmitted byapplying the T-RPT pattern on the timing departing from k subframe fromDCI transmission timing.

Here, k corresponds to 6.

In the case that the timing of transmitting data by applying the T-RPTpattern is defined as the timing departing as much as k′ subframe fromthe SA transmission timing, k′ corresponds to 2.

However, in some cases, a case may occur that (the first) SA istransmitted on timing later than (the first or the later) datatransmission timing.

Accordingly, in order to prevent it, as shown in FIG. 22, the first bit2210 having ‘1’ value for the first time in the T-RPT pattern issynchronized with the SA transmission timing (SF #n+6, 2220). In thiscase, the SA and (the first) data may be transmitted with being FDMed.

That is, FIG. 22 illustrates another method for determining atransmission timing of data using T-RPT pattern proposed in the presentdisclosure.

In addition, it is defined that the remaining bits of the T-RPT patterncorresponds to (re)transmission timing of data.

Here, the remaining bits of the T-RPT pattern represent the bits afterthe first bit having ‘1’ value for the first time in the T-PRT pattern.

That is, in the case that total x bits having ‘1’ value are existed inthe T-RPT pattern, 1 bit among the total x bits indicates SAtransmission, and the remaining (x−1) bit(s) indicates (re)transmissionof data. In this case, it means that data is (re)transmitted (x−1)times.

Second Embodiment: Not Using T-RPT Field

The second embodiment relates to a method of using another field, notusing the T-RPT field included in the DCI of Sidelink communication forthe DCI of V2X Sidelink communication.

The second embodiment may be more efficient than the first embodiment inthe following reasons.

First, since it is required to reduce a size of the DCI in V2X Sidelinkcommunication (Mode 3 and Mode 4), it is preferable to define a newfield having a bit number smaller than that of the T-RPT field using 7bits in the existing Sidelink communication.

The reason is because there is not so such data transmission amount forV2X Sidelink communication and a problem that resource is wasted mayoccur in the case that resource is allocated using the existing T-RPT.

In addition, since mobility is added when a UE drives in fast speed inthe V2X Sidelink communication, in the case that resource is allocatedin the existing T-RPT pattern method, the V2X Sidelink communication maynot be properly performed.

In the case that several elements constructing T-RPT, for example, anumber of repetition transmissions or repeatedly transmitted pattern islimited to a predetermined number, all T-RPT patterns may not berequired. That is, this may mean that resource flexibility is not sogreat.

Accordingly, in this case, a method of newly defining and using otherfields (e.g., other indicators) performing the same operation may beconsidered than using the T-RPT.

As described above, when the indicators other than the T-RPT field areused, the transmission pattern of the data can be represented with asmaller number of bits than using the T-RPT field (7 bits).

For example, in the case that retransmission data is transmitted in aconsecutive TTI or with a fixed/uniform (same interval) interval, theT-RPT pattern described above is not required to be used.

As such, the fixed/uniform (same interval) interval of timing offset maybe predefined, indicated through RRC signaling in the case of beingvariable, or indicated through a part of fields of the DCI.

The T-RPT pattern defined in LTE Rel-12 is defined to perform all dataretransmissions within 8 TTIs, basically.

However, even in the case that it is not available to perform all dataretransmissions within 8 TTIs, it may not be proper to use the T-RPTpattern described above.

As an example of this, in order for all UEs to have (re)transmissionpatterns which are orthogonal with each other in time domain, it needsto be more widely spread on time domain.

However, in the case that a range that UEs may (re)transmit in timedomain is limited, a probability that collision between transmissiondata occurs (i.e., transmitted in the same TTI) becomes high.

Accordingly, it may not be proper to use the T-RPT pattern in such acase.

Therefore, hereinafter, a method for (re)transmitting data using a timeoffset related indicator, not the T-RPT pattern, is described in detail.

That is, in the case that it is not available to use the existing T-RPT,new time offset related indicators may be defined which may perform thesame or similar operation (or function) as the T-RPT.

The time offset related indicator is information indicating a timing gapor an offset between an initial data transmission and retransmissiondata.

In addition, the time offset related indicator may also be interpretedas information indicating a timing gap between data.

At this time, types of the information that may be indicated through theexisting T-RPT may include (1) number of repetition transmissions, (2) atiming gap between a data transmission and (the next) data transmission(e.g., retransmission), and the like.

In the case of not using the T-RPT, a particular method for indicatinginformation of (1) and (2) is required, which is described below.

In section (2), the data transmission may mean an initial transmission,and (the next) data transmission may mean a retransmission

In addition, unless the case that DCI is transmitted in every (data)(re)transmission, in addition to information of (1) and (2), thefollowing information is also required to be determined.

Further, in the case that the following information does not use theT-RPT similarly, a method of indicating it to a UE may be required.

-   -   Timing gap between SA transmission and (associated) data        transmission    -   Timing gap between SA transmission and (the next) SA        transmission

Furthermore, in addition to the method of indicating a time-frequencyindex on which SA is to be transmitted through the existing SA resource(or resource for PSCCH), a time resource and a frequency resource of SAmay be divided and indicated.

In this case, a method of determining information such as SA (initial)transmitting timing may also be required.

Then, a method for configuring or indicating time resource informationrepresenting a time resource for data (re)transmission or a specificform of the time resource, not using the T-RPT pattern, will bedescribed.

Here, the time resource information may include indicators related to atiming offset.

That is, in the case that the T-RPT described in the first embodiment isnot used for data (re)transmission in the V2X Sidelink communication,information needs to be configured or indicated, such as (1) number ofrepetition transmissions, (2) SA (initial) transmission timing, (3) atiming gap between SA transmission and (associated) data transmission,(4) a timing gap between data transmission and (the next) datatransmission, and the like. At least one of (1) to (4) may be includedin the time resource information.

In the case that the T-RPT is not used, a method for indicating orconfiguring each of the information of (1) to (4) will be described indetail.

First, the number of repetition transmissions is described.

The number of repetition transmissions may represent a count of databeing repeated or retransmitted.

In the case that the T-RPT is used, the information for data number ofrepetition transmissions is implicitly mapped in the T-RPT.

However, in the case that the T-RPT is not used, the number ofrepetition transmissions of data may be indicated or configured by usingthe message set of Table 3 described above.

In the case that the message set is not included in the DCI or notsignaled to a UE, the number of repetition transmissions may beindicated through RRC signaling or a part of bits of the DCI may be usedfor the use of informing the number of repetition transmissions.

Here, the information or the field indicating the number of repetitiontransmissions may be represented as N_rpt field, for example.

Next, SA (initial) transmission timing is described.

The SA (initial) transmission timing may be preferred to use a method ofindicating or determining how much degree of offset is departed withreference to a specific timing (as a reference) rather than indicating aspecific absolute value of a timing when SA is transmitted.

For example, in the case that an eNB transmits the DCI to a transmissionUE on n^(th) subframe (SF #n), it may be defined that the associated SAis transmitted on n+4^(th) subframe (SF #n+4) or the first Sidelinksubframe generated after the SF #n+4.

The Sidelink subframe means a subframe on which the SA or data can betransmitted, and may be represented as Sidelink Control (SC) period.

The expression ‘A and/or B’ used in the present disclosure may beidentically interpreted as the meaning of ‘at least one of A or B’.

As such, in the case that SA transmission timing is defined, an eNB mayindicate only the frequency resource allocation information for the SAtransmission to a UE.

Subsequently, the timing gap between SA transmission and (associated)data transmission is described.

When a specific message is generated (from a specific UE), until thetiming when a reception UE receives the generated specific message, alatency time occurs (in physical layer) including 1) timing gap betweenthe message generation time and the DCI transmission time, 2) timing gapbetween the DCI transmission time and the SA transmission time, and 3)timing gap between the SA transmission time and the Data transmissiontime.

It needs to configure a timing gap between the data transmissions suchthat the summation of the timing gaps of sections 1) to 3) becomes notto great considering latency requirements for the message transmission.

For example, assuming that each of the timing gap between the DCItransmission time and the SA transmission time and the timing gapbetween the SA transmission time and the Data transmission time is 4TTIs, there exists latency time of 8 TTIs already owing to the twotiming gaps.

Accordingly, it is required to define or configure such that the timinggaps between the SA transmission time and the Data transmission timedoes not have too great value.

In other words, this may mean that a range of fluctuation of the timinggap is not too great.

Accordingly, the following two methods (method 1 and method 2) may beconsidered such that the timing gaps between the SA transmission timeand the Data transmission time does not have too great value.

(Method 1)

First, method 1 uses the timing gap from the SA transmission time to theData transmission time as a value which is common to all UEs and apredefined fixed value.

The fact that the range of fluctuation of the corresponding timing gap(from the SA transmission time to the Data transmission time) is not toogreat may be interpreted that it does not have a significant meaning toconfigure the corresponding timing gap value in UE-specific manner.

Accordingly, it may be defined such that all UEs use a predefined fixedvalue.

(Method 2)

Method 2 uses the timing gap from the SA transmission time to the Datatransmission time in UE-specific manner.

As described above, method 2 may be used for the case that it isrequired to distinguish UEs using UE-specific values or the case that itis required to allocate data resource to be flexible to the maximum.

Method 2 may be divided into method {circle around (1)} and method{circle around (2)} as below.

First, method {circle around (1)} is to indicate the timing gap from theSA transmission time to the Data transmission time through RRC signalingor inform using a part of bits of the DCI.

In the case that the DCI is transmitted in every (data)(re)transmission, this value may be designated through the correspondingfield in each DCI, and in the case that the DCI is transmitted once forall (data) (re)transmissions, the timing gap value may be identicallyapplied to all (re)transmissions through the corresponding field.

On the other hand, method {circle around (2)} uses the timing gap fromthe SA transmission time to the Data transmission time designated in theSA, not informing directly the timing gap from the SA transmission timeto the Data transmission time through the DCI.

Whether to use the timing gap from the SA transmission time to the Datatransmission time designated in the SA, it may be indicated orconfigured through 1 bit flag and the like in the DCI.

For example, in the case that the 1 bit flag in the DCI is configured as‘1’, a transmission UE transmits data to a reception UE with an offsetas much as the timing gap designated in the SA.

Here, the SA may designate a timing gap value for one or more datatransmissions.

More particularly, the timing gap value for the one or more datatransmissions may be determined by using the T-RPT value of the SA.

That is, assuming that a position of each bit of the T-RPT indicates arelative timing gap from the SA transmission time, the fact that aspecific bit(s) of the T-RPT is configured as ‘1’ may mean the data istransmitted on the timing departed as much as the corresponding TTI fromthe SA.

In other words, the timing when ‘1’ value is generated for the firsttime (or firstly) in the T-RPT pattern may be the timing gap between theSA and (the first or associated) data transmission times.

For example, the timing when ‘1’ value is generated for the first time(or firstly) in the T-RPT pattern is on the first bit (i.e., MSB bit),this may mean that the SA and the data are transmitted on the sametiming (or same subframe). In this case, the SA and the data may betransmitted with being FDMed.

Alternatively, in the case that the 1 bit flag in the DCI is ‘0’, it maybe interpreted that the timing gap value designated in the SA is notused.

For example, a data transmission time may be determined by using atiming gap field indicating the timing gap from the SA transmission timeto the Data transmission time designated in the DCI.

For another example, it may be configured that the SA and the data maybe transmitted on the same time, that is, FDMed.

That is, this may mean that the SA and the data are transmitted on thesame subframe.

In this case, the 1 bit flag in the DCI may be used as an indicator fordistinguishing FDM and TDM between the SA and the data.

Next, a timing gap between a data transmission and (the next) datatransmission is described.

Similar to the timing gap between the SA transmission and the(associated) data transmission, it is required to configure such thatthe value becomes not too great (or a range of fluctuation of thecorresponding timing gap is not too great) considering the latencyrequirement and the like of a message transmission.

Accordingly, the same or similar method may be applied with the schemeof designating the timing gap from the SA transmission time to the datatransmission time described above.

That is, firstly, a method may be applied by using the correspondingvalue (timing gap between data transmission and (the next) datatransmission to a value which is common between UEs and predefined fixedvalue.

Here, the fact that the range of fluctuation of the corresponding valueis not too great means that it does not have significant meaning toconfigure it in UE-specific manner, and it may be considered to use apredefined value commonly for all UEs.

Secondly, a UE-specific value is used.

That is, in the case that UEs needs to be distinguished by UE-specificvalue, or in the case that data resource allocation has to be performedin flexible manner to the maximum, the UE-specific value may be used.

Even in this case, method {circle around (1)} and method {circle around(2)} of method 2 described above may be identically applied.

That is, like the method {circle around (1)}, the timing gap betweendata and (the next) data transmission times may be indicated through RRCsignaling or indicated by using a part of bits of the DCI. In this case,this value may be indicated again through the SA.

In the case that the DCI is transmitted in every (data)(re)transmission, this value may be designated through the correspondingfield for each DCI, and in the case that the DCI is transmitted onlyonce for all (data) (re)transmissions, the timing gap value may beidentically applied to all (re)transmissions through the correspondingfield.

In addition, like the method {circle around (2)}, the timing gap valuebetween data and (the next) data transmission times is not directlyinformed through the DCI, but the timing gap indicating the timing gapfrom the data transmission time and (the next) data transmission timedesignated in the SA may be applied.

Further, whether the timing gap between the data transmission time andthe next data transmission time designated in the SA may be indicated orconfigured through the 1 bit field in the DCI.

For example, in the case that the 1 bit flag in the DCI is value ‘1’, atransmission UE transmits (the next) data to a reception UE with anoffset as much as the timing gap designated in the SA.

The SA may designate a timing gap value for one or more datatransmissions.

More particularly, the timing gap value between data transmissions maybe determined by using the T-RPT value of the SA.

Alternatively, in the case that the 1 bit flag in the DCI is ‘0’, it maybe interpreted that the timing gap value designated in the SA is notused.

For example, a data transmission time may be determined by using atiming gap field between data and (the next) data designated in the DCI.

A part or the whole of the predefined values described above, RRCsignaling and DCI fields may be selectively combined and used.

As another embodiment, in the case that resource allocations betweendynamic scheduling and SPS scheduling is overlapped, a method forsolving it is described.

A part or the whole of the timing when data (re)transmission of dynamicscheduling is generated and the timing when data (re)transmission isgenerated by SPS (or timing when the corresponding resource isallocated) in a specific UE aspect may be overlapped.

In this case, in the case that different UEs transmit datasimultaneously (in the same TTI or the same subframe), problems such ashalf-duplex, resource collision and interference increase may occur.

Accordingly, a method may be required such that two types oftransmissions are not generated simultaneously.

In the case that two transmissions are generated simultaneously, it maybe defined to select one of the three methods as below according tomessage type, application or use case.

First, the first method is to follow resource allocation of dynamicscheduling.

That is, the first method is to follow the resource allocation ofdynamic scheduling in the case that SPS transmission period is not long(e.g., 10 ms) and/or more urgent and important message is transmittedthrough dynamic scheduling.

At this time, the transmission data for dropped SPS (or of whichtransmission time is missed) may be dropped as it is according toimportance or urgency, or may be allocated again in other timing throughSPS reconfiguration, scheduling request (for SPS resource allocation).

Next, the second method is to follow the resource allocation of SPSscheduling.

That is, the second method is to follow the SPS scheduling method in thecase that the SPS transmission period is relatively long (e.g., 500 ms)and more urgent and importance message is transmitted through serioustransmission latency and/or SPS scheduling once the SPS transmission isdropped.

Next, the third method is to follow a priority of the message (orpacket).

That is, the third method is to determine the way of resource allocationaccording to a priority order provided for each message (or packet) inthe case that the priority may not be determined only with dynamicscheduling or SPS scheduling scheme simply.

In the case that the priority is the same, scheduling scheme may bedetermined in random way.

FIG. 23 is a flowchart illustrating an example of a method fortransmitting and receiving data in V2X Sidelink communication proposedin the present disclosure.

Referring to FIG. 23, a method is described for a first UE to transmitSidelink related data to a second UE through sidelink in a wirelesscommunication system supporting Vehicle-to-Everything (V2X)communication.

First, the first UE receives, from a base station, Downlink ControlInformation (DCI) including information related to a transmission offirst control information (step, S2310).

The DCI may also include information for transmission data in additionto the information for the first control information.

In addition, the DCI may include a part of the contents of the firstcontrol information.

Further, the DCI may be represented as DCI format 5A inVehicle-to-Everything (V2X) Sidelink communication.

The first control information is information used for scheduling datatransmitted (or to be transmitted) to the second UE, and may beinformation indicating resource allocation information for data to betransmitted for selecting Sidelink resource or scheduling.

The first control information may be represented Scheduling Assignment(SA), Physical Sidelink Control Channel (PSCCH) and the like.

Here, the first UE may mean a transmission UE, and the second UE maymean a reception UE.

In addition, the DCI is transmitted in subframe #n, and the firstcontrol information may be transmitted in subframe #n+k or in a specificsidelink subframe generated after the subframe #n+k.

The k may be 4.

Here, the specific side link subframe may be the first side linksubframe (s) occurring after the (n+k) th subframe.

Here, the specific Sidelink subframe may be Sidelink subframe(s)included in Sidelink period firstly usable which is started aftersubframe #n+k.

The Sidelink period may be represented as SC period.

In addition, the DCI may include second control information indicating atiming gap between the first data transmission and the second datatransmission, and may include the information mentioned in the secondembodiment described above.

The second control information may indicate a timing gap field,

and included in the first control information.

Later, the first UE transmits, to the second UE, the first controlinformation based on the received DCI (step, S2320).

Later, the first UE transmits, to the second UE, one or more datathrough the sidelink (step, S2330).

The first control information and the one or more data may betransmitted on an identical timing, and the identical timing may mean anidentical subframe.

Further, the first data transmission may mean an initial transmission ofdata, and the second data transmission may mean a retransmission ofdata.

Overview of Devices to Which the Present Invention Can be Applied

FIG. 24 illustrates a block diagram of a wireless communication deviceto which the methods proposed in the present disclosure may be applied.

Referring to FIG. 24, a wireless communication system includes a basestation (or eNB) 2410 and a plurality of terminals (or UEs) 2420 locatedwithin coverage of the eNB 2410.

The eNB 2410 includes a processor 2411, a memory 2412, and a radiofrequency (RF) unit 2413. The processor 2411 implements functions,processes and/or methods proposed in FIG. 1 to FIG. 23. Layers of radiointerface protocols may be implemented by the processor 2411. The memory2412 may be connected to the processor 2411 to store various types ofinformation for driving the processor 2411. The RF unit 2413 may beconnected to the processor 2411 to transmit and/or receive a wirelesssignal.

The UE 2420 includes a processor 2421, a memory 2422, and a radiofrequency (RF) unit 2423.

The processor 2421 implements functions, processes and/or methodsproposed in FIG. 1 to FIG. 23. Layers of radio interface protocols maybe implemented by the processor 2421. The memory 2422 may be connectedto the processor 2421 to store various types of information for drivingthe processor 2421. The RF unit 2423 may be connected to the processor2421 to transmit and/or receive a wireless signal.

The memory 2412 or 2422 may be present within or outside of theprocessor 2411 or 2421 and may be connected to the processor 2411 or2421 through various well known units.

For example, in order to transmit and receive data between UEs in awireless communication system supporting V2X communication, the UE mayinclude a Radio Frequency (RF) unit for transmitting and receiving aradio signal; and a processor functionally connected to the RF unit.

Also, the eNB 2410 and/or the UE 2420 may have a single antenna ormultiple antennas.

FIG. 25 illustrates a block diagram of a wireless communicationapparatus according to an embodiment of the present invention.

Particularly, in FIG. 25, the UE described above FIG. 24 will beexemplified in more detail.

Referring to FIG. 25, the UE includes a processor (or digital signalprocessor) 2510, RF module (RF unit) 2535, power management module 2505,antenna 2540, battery 2555, display 2515, keypad 2520, memory 2530,Subscriber Identification Module (SIM) card 2525 (which may beoptional), speaker 2545 and microphone 2550. The UE may include a singleantenna or multiple antennas.

The processor 2510 may be configured to implement the functions,procedures and/or methods proposed by the present invention as describedin FIG. 1 to FIG. 23. Layers of a wireless interface protocol may beimplemented by the processor 2510.

The memory 2530 is connected to the processor 2510 and storesinformation related to operations of the processor 2510. The memory 2530may be located inside or outside the processor 2510 and may be connectedto the processors 2510 through various well-known means.

A user enters instructional information, such as a telephone number, forexample, by pushing the buttons of a keypad 2520 or by voice activationusing the microphone 2550. The microprocessor 2510 receives andprocesses the instructional information to perform the appropriatefunction, such as to dial the telephone number. Operational data may beretrieved from the SIM card 2525 or the memory module 2530 to performthe function. Furthermore, the processor 2510 may display theinstructional and operational information on the display 2515 for theuser's reference and convenience.

The RF module 2535 is connected to the processor 2510, transmits and/orreceives an RF signal. The processor 2510 issues instructionalinformation to the RF module 2535, to initiate communication, forexample, transmits radio signals comprising voice communication data.The RF module 2535 comprises a receiver and a transmitter to receive andtransmit radio signals. An antenna 2540 facilitates the transmission andreception of radio signals. Upon receiving radio signals, the RF module2535 may forward and convert the signals to baseband frequency forprocessing by the processor 2510. The processed signals would betransformed into audible or readable information outputted via thespeaker 2545.

The aforementioned embodiments are achieved by combination of structuralelements and features of the present invention in a predeterminedmanner. Each of the structural elements or features should be consideredselectively unless specified separately. Each of the structural elementsor features may be carried out without being combined with otherstructural elements or features. Also, some structural elements and/orfeatures may be combined with one another to constitute the embodimentsof the present invention. The order of operations described in theembodiments of the present invention may be changed. Some structuralelements or features of one embodiment may be included in anotherembodiment, or may be replaced with corresponding structural elements orfeatures of another embodiment. Moreover, it will be apparent that someclaims referring to specific claims may be combined with another claimsreferring to the other claims other than the specific claims toconstitute the embodiment or add new claims by means of amendment afterthe application is filed.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreASICs (Application Specific Integrated Circuits), DSPs (Digital SignalProcessors), DSPDs (Digital Signal Processing Devices), PLDs(Programmable Logic Devices), FPGAs (Field Programmable Gate Arrays),processors, controllers, microcontrollers, microprocessors, etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in the memory and executed bythe processor. The memory may be located at the interior or exterior ofthe processor and may transmit data to and receive data from theprocessor via various known means.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come

1. A method for transmitting data through sidelink in a wireless communication system supporting Vehicle-to-Everything (V2X) communication, the method performed by a first User Equipment comprising: receiving, from a base station, Downlink Control Information (DCI) including information related to a transmission of first control information, wherein the first control information is used for scheduling data transmitted to a second User Equipment; transmitting, to the second User Equipment, the first control information based on the received DCI; and transmitting, to the second User Equipment, one or more data through the sidelink, wherein the DCI is transmitted in subframe #n, wherein the first control information is transmitted in subframe #n+k or in a specific sidelink subframe generated after the subframe #n+k, and wherein the DCI includes second control information indicating a timing gap between a first data transmission and a second data transmission and wherein the second control information is a timing gap field.
 2. The method of claim 1, wherein the k is
 4. 3. The method of claim 1, wherein the first control information and the one or more data are transmitted to the second User Equipment on an identical timing.
 4. The method of claim 3, wherein the identical timing is an identical subframe.
 5. The method of claim 1, wherein the first data transmission is an initial transmission of data, and wherein the second data transmission is a retransmission of data.
 6. The method of claim 1, wherein the first control information is a Scheduling Assignment (SA).
 7. (canceled)
 8. The method of claim 1, wherein the first control information includes the second control information.
 9. The method of claim 1, wherein the specific sidelink subframe includes initial sidelink subframes generated after the subframe #n+k.
 10. The method of claim 1, when resource allocations for the one or more data are scheduled simultaneously by Dynamic Scheduling and Semi-Persistent Scheduling (SPS), wherein either one of the Dynamic Scheduling and the SPS is applied based on a specific criterion.
 11. The method of claim 10, wherein the specific criterion includes at least one of a length of transmission period of the SPS or an importance of transmission data.
 12. A first User Equipment for transmitting data through sidelink in a wireless communication system supporting Vehicle-to-Everything (V2X) communication, the first User Equipment comprising: a Radio Frequency (RF) unit configured to transmit and receive a radio signal; and a processor functionally connected with the RF unit, wherein the processor is configured to perform: receiving, from a base station, Downlink Control Information (DCI) including information related to a transmission of first control information, wherein the first control information is used for scheduling data transmitted to a second User Equipment; transmitting, to the second User Equipment, the first control information based on the received DCI; and transmitting, to the second User Equipment, one or more data through the sidelink, wherein the DCI is transmitted in subframe #n, wherein the first control information is transmitted in subframe #n+k or in a specific sidelink subframe generated after the subframe #n+k, wherein the DCI includes second control information indicating a timing gap between a first data transmission and a second data transmission, and wherein the second control information is a timing gap field.
 13. The first User Equipment of claim 12, wherein the k is
 4. 14. The first User Equipment of claim 12, wherein the first control information and the one or more data are transmitted to the second User Equipment on an identical timing.
 15. The first User Equipment of claim 14, wherein the identical timing is an identical subframe.
 16. The first User Equipment of claim 12, wherein the first data transmission is an initial transmission of data, and wherein the second data transmission is a retransmission of data.
 17. (canceled)
 18. The first User Equipment of claim 12, wherein the first control information includes the second control information.
 19. The first User Equipment of claim 12, wherein the specific sidelink subframe includes initial sidelink subframes generated after the subframe #n+k. 